Restore memory perms on svcUnmapMemory/UnloadNro

Prior to PR, Yuzu did not restore memory to RW-
on unmap of mirrored memory or unloading of NRO.

(In fact, in the NRO case, the memory was unmapped
instead of reprotected to --- on Load, so it was
actually lost entirely...)

This PR addresses that, and restores memory to RW-
as it should.

This fixes a crash in Super Smash Bros when creating
a World of Light save for the first time, and possibly
other games/circumstances.