MIPS: Add support for FTLBs

MIPS: Add support for FTLBs

The Fixed Page Size TLB (FTLB) is a set-associative dual entry TLB. Its
purpose is to reduce the number of TLB misses by increasing the effective
TLB size and keep the implementation complexity to minimum levels.
A supported core can have both VTLB and FTLB.

Reviewed-by: James Hogan <[email protected]>
Reviewed-by: Paul Burton <[email protected]>
Signed-off-by: Leonid Yegoshin <[email protected]>
Signed-off-by: Markos Chandras <[email protected]>
Signed-off-by: John Crispin <[email protected]>
Patchwork: http://patchwork.linux-mips.org/patch/6139/