fix(arm): only expose `arm_bl2_dyn_cfg_init` to BL2

The `arm_bl2_dyn_cfg_init` function is intended exclusively for BL2 - it
should not be compiled for any other bootloader image. This change hides
it for all but BL2.

Change-Id: I9fa95094dcc30f9fa4cc7bc5b3119ceae82df1ea
Signed-off-by: Chris Kay <chris.kay@arm.com>
2 files changed