MIPS: mm: c-r4k: Detect instruction cache aliases

The *Aptiv cores can use the CONF7/IAR bit to detect if the core
has hardware support to remove instruction cache aliasing.

This also defines the CONF7/AR bit in order to avoid using
the '16' magic number.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6499/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

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

diff --cc arch/mips/mm/c-r4k.c
Simple merge