ArmPkg/Mmu: Fix page level calculation bug
ArmPkg/Mmu: Fix page level calculation bug

The bug can be triggered when alignment of Base is larger than Length
by 2 level of page granularity, e.g.

Base is 0x4000_0000, Length is 0x1000

The original code will change 2MB page level and we will get a
negative remaining length.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

git-svn-id: 3158a46dfd52e07d1fda3e32e1ab2e353a00b20f@18422 6f19259b-4bc3-4df7-8a09-765794883524

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2