riscv: add more dump features to GENERIC

[mhorne]

Summary

Match what is provided by default on other architectures.

[jrtc27]

amd64, arm64, i386, powerpc, powerpc64 and powerpc64le all have this exact set in their GENERIC (or suffixed) configs, so seems sensible to me. Oh to have a shared std.generic etc in sys/conf!

sys/riscv/conf/GENERIC

if (rsdp->Revision >= 2 && rsdp->XsdtPhysicalAddress != 0) {
                 /*
                  * AcpiOsGetRootPointer only verifies the checksum for
                  * the version 1.0 portion of the RSDP.  Version 2.0 has
                  * an additional checksum that we verify first.
                  */
                 if (AcpiTbChecksum((UINT8 *)rsdp, ACPI_RSDP_XCHECKSUM_LENGTH)) {
                         if (bootverbose)
                                 printf("ACPI: RSDP failed extended checksum\n");
+                        pmap_unmapbios((vm_offset_t)rsdp,
+                            sizeof(ACPI_TABLE_RSDP));
                         return (0);
                 }
                 xsdt = map_table(rsdp->XsdtPhysicalAddress, ACPI_SIG_XSDT);
                 if (xsdt == NULL) {
                         if (bootverbose)
                                 printf("ACPI: Failed to map XSDT\n");
+                        pmap_unmapbios((vm_offset_t)rsdp,
+                            sizeof(ACPI_TABLE_RSDP));
                         return (0);
                 }
                 count = (xsdt->Header.Length - sizeof(ACPI_TABLE_HEADER)) /
                     sizeof(UINT64);
                 for (i = 0; i < count; i++)
                         if (probe_table(xsdt->TableOffsetEntry[i], sig)) {
                                 addr = xsdt->TableOffsetEntry[i];
                                 break;
                         }
                 acpi_unmap_table(xsdt);
         } else {
                 rsdt = map_table(rsdp->RsdtPhysicalAddress, ACPI_SIG_RSDT);
                 if (rsdt == NULL) {
                         if (bootverbose)
                                 printf("ACPI: Failed to map RSDT\n");
+                        pmap_unmapbios((vm_offset_t)rsdp,
+                            sizeof(ACPI_TABLE_RSDP));
                         return (0);
                 }
                 count = (rsdt->Header.Length - sizeof(ACPI_TABLE_HEADER)) /
                     sizeof(UINT32);
                 for (i = 0; i < count; i++)
                         if (probe_table(rsdt->TableOffsetEntry[i], sig)) {
                                 addr = rsdt->TableOffsetEntry[i];
                                 break;