Add uppercase macro to build_macros.mk
Yatharth Kochar authored
This patch adds `uppercase` macro to prepare IMAGE_BLxx defines
used for conditional compilation and to prepare variables used
for defining BL source and linker file names.

This change is needed for upcoming BL images that can have names
which uses both letters and numbers.

Change-Id: I05ce9bcd0d221a54db92c0fe3ad28e9e0080ed2e
5ba8f669