arm: Expand SMCCC arguments and return values

PSCI uses the SMC Calling Convention (SMCCC) to communicate with the higher
level software. PSCI uses at most 4 arguments and expend only one return
value. However, SMCCC has provisions for more arguments (upto 17 depending
on the SMCCC version) and upto 10 distinct return values.

We are going to be adding tests that make use of it, so add support for the
extended number of arguments and return values.

Also rename the SMCCC functions to generic, non-PSCI names, so they
can be used for Realm services.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
[ Expand the number of args to 11 /results 10]
Signed-off-by: Joey Gouly <joey.gouly@arm.com>