arm64: Initialize TLB memory if CMO_BY_VA_ONLY

Memory used to hold the page tables is allocated from the top of RAM
with no prior initialization and could therefore hold invalid data. As
invalidate_dcache_all() will be called before the MMU has been
initialized and as that function relies indirectly on the page tables
when using CMO_BY_VA_ONLY, these must be in a valid state from their
allocation.

Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>
[ Paul: pick from the Android tree. Fix checkpatch warnings, and rebased
  to the upstream. ]
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: Tom Rini <trini@konsulko.com>
Link: https://android.googlesource.com/platform/external/u-boot/+/e3ceef4230b772186c6853cace4a676a407e6ab7