xtensa: allow fixmap and kmap span more than one page table

To support aliasing cache both kmap region sizes are multiplied by the
number of data cache colors. After that expansion page tables that cover
kmap regions may become larger than one page. Correctly allocate and
initialize page tables in this case.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

diff --cc arch/xtensa/mm/mmu.c
Simple merge