Increase default EFI staging area size from 32MB to 48MB.

[jhb]

Summary

The EFI boot loader allocates a single chunk of contiguous memory to
hold the kernel, modules, and any other loaded data. This memory block
is relocated to the kernel's expected location during the transfer of
control from the loader to the kernel.

The GENERIC kernel on amd64 has recently grown such that a kernel + zfs.ko
no longer fits in the default staging size. Bump the default size from
32MB to 48MB to provide more breathing room.

PR: 201679

[jhb]

Andrew, I'm not sure if a default size of 48MB is ok for aarch64? For amd64 I suspect any machine with 64MB of RAM should be able to support this.

Also, this file has several hardcoded '4096' values. Should it be ok to use PAGE_SIZE directly instead (or is there an EFI constant that is the equivalent of PAGE_SIZE?)

Hmm, there is EFI_PAGE_SIZE and friends in efidef.h. It is currently hardcoded as 4096.

[imp]

This looks good, modulo the 4096 hard coding issue that was pre-existing..