Remove SMCCC_MINOR/MAJOR_VERSION macros

The purpose of these macros is unclear - is it tracking the exact
SMCCC version expected by the TF-A Tests, or the maximum version, or
something else? Besides, they are not used in the source tree so
better to remove them as to avoid any confusion.

Change-Id: Ieb426dc9c54f19b0907d3221bb5606e03c9e360f
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>