Calculate TCR bits based on VA and PA

Currently the TCR bits are hardcoded in xlat_tables.c. In order to
map higher physical address into low virtual address, the TCR bits
need to be configured accordingly.

This patch is to save the max VA and PA and calculate the TCR.PS/IPS
and t0sz bits in init_xlat_tables function.

Change-Id: Ia7a58e5372b20200153057d457f4be5ddbb7dae4
Merge pull request #161 from danh-arm/lm/calc-tcr-bits

Calculate TCR bits based on VA and PA