ti: k3: common: Remove unused STUB macro
ti: k3: common: Remove unused STUB macro

This macro was used when many of these functions were stubbed out,
the macro is not used anymore, remove it.

Signed-off-by: Andrew F. Davis <a6dfde0ec5c5124d26ab0cb4f9ab9a758dee1d6f@ti.com>
Change-Id: Ida33f92fe3810a89e6e51faf6e93c1d2ada1a2ee

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware