arm: PSCI: use definitions provided by asm/smccc.h

arm: PSCI: use definitions provided by asm/smccc.h

smccc.h provides definitions to construct SMC call function number according
to SMCCC. We don't need multiple definitions for one thing, and definitions
in smccc.h are more generic than ones used in psci.h.

So psci.h will only provide function codes, while whole SMC function
identifier will be constructed using generic macros from smccc.h.

Function psci_mode_check() in vsmc.c will be removed in a next patch,
so there are no need to review it. I had to rework it, because
PSCI_0_2_64BIT definition is dropped now.

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Acked-by: Julien Grall <julien.grall@arm.com>