MIPS: Use generic checksum functions for MIPS R6

The following instructions have been removed from MIPS R6

ulw, ulh, swl, lwr, lwl, swr.

However, all of them are used in the MIPS specific checksum implementation.
As a result of which, we will use the generic checksum on MIPS R6

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

diff --cc arch/mips/Kconfig
Simple merge

diff --cc arch/mips/include/asm/Kbuild
Simple merge

diff --cc arch/mips/include/asm/checksum.h
Simple merge

diff --cc arch/mips/kernel/mips_ksyms.c
Simple merge

diff --cc arch/mips/lib/Makefile
Simple merge