psci: add features/reset2 support

psci: add features/reset2 support

Adds support for:
* PSCI_FEATURES, which was introduced in PSCI 1.0. This provides API
that allows discovering whether a specific PSCI function is implemented
and its features.
* SYSTEM_RESET2, which was introduced in PSCI 1.1, which extends existing
SYSTEM_RESET. It provides support for vendor-specific resets, providing
reset_type as an additional param.

For additional details visit [1].

Implementations of some functions were borrowed from Linux PSCI driver
code [2].

[1] https://developer.arm.com/documentation/den0022/latest/
[2] drivers/firmware/psci/psci.c

Signed-off-by: Igor Opaniuk <igor.opaniuk@foundries.io>