MIPS: Merge the identical "return from syscall" per-ABI code

No need to keep 4 copies of that stuff; merged and taken to
entry.S, unused public symbols there killed off.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --cc arch/mips/kernel/entry.S
Simple merge

diff --cc arch/mips/kernel/scall32-o32.S
Simple merge

diff --cc arch/mips/kernel/scall64-64.S
Simple merge

diff --cc arch/mips/kernel/scall64-n32.S
Simple merge

diff --cc arch/mips/kernel/scall64-o32.S
Simple merge