QcomModulePkg: Set the right Compiler optimization flag

Set the compiler optimization flag from conf settings and use Oz by
default for debug builds. Oz is combination of O2 and Os, does an
aggresssive size optimization. Remove the O2 setting from dec and
inf files.

CRs-Fixed: 1080079
Change-Id: I668a2cd278152ad63c9bca56fd75ca1c6bb6046e
4 files changed