Fix build error with optimizations disabled (-O0)

Fix build error with optimizations disabled (-O0)

If Trusted Firmware is built with optimizations disabled (-O0), the
linker throws the following error:

    undefined reference to 'xxx'

Where 'xxx' is a raw inline function defined in a header file. The
reason is that, with optimizations disabled, GCC may decide to skip
the inlining. If that is the case, an external definition to the
compilation unit must be provided. Because no external definition
is present, the linker throws the error.

This patch fixes the problem by declaring the following inline
functions static, so the internal definition is used:
 - cm_set_next_context()
 - bakery_lock_init()

Note that building the TF with optimizations disabled when Trusted
Board Boot is enabled is currently unsupported, as this makes the BL2
image too big to fit in memory without any adjustment of its base
address. Similarly, disabling optimizations for debug builds on FVP
is unsupported at the moment.

Change-Id: I284a9f84cc8df96a0c1a52dfe05c9e8544c0cefe