RISC-V: un-ifdef vm.kvm_size and vm.kvm_free sysctls

[mhorne]

Summary

While here, remove some trailing whitespace.

Test Plan

sysctl output:

root@qemu:~ # sysctl vm.kvm_size
vm.kvm_size: 34359738368
root@qemu:~ # sysctl vm.kvm_free
vm.kvm_free: 33460060160

[markj]

sys/riscv/riscv/pmap.c

1445–1446

While here, perhaps add a space around '|' and add CTLFLAG_MPSAFE. Otherwise Giant will be acquired around each call to the handler. There is some work in progress to invert the default behaviour wrt Giant, but adding the flag now will reduce the number of handlers that need to be audited.

[mhorne]

Add CTLFLAG_MPSAFE. Move sysctl description to a separate line.