arm64: Remove unused definitions from asm/unistd32.h

This patch removes the compat __NR_* definitions from the unistd32.h
file and only keeps those that are used by the AArch64 kernel with a new
__NR_compat_* prefix. The additional wrapper definitions in
arch/arm64/kernel/sys32.S have been removed and the actual wrapper names
included in the asm/unistd32.h file.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>