riscv: Enable PM_GENERIC_DOMAINS for T-Head SoCs

riscv: Enable PM_GENERIC_DOMAINS for T-Head SoCs

T-Head SoCs feature separate power domains (power islands) for major
components like the GPU, Audio, and NPU. To manage the power states of
these components effectively, the kernel requires generic power domain
support.

This commit enables `CONFIG_PM_GENERIC_DOMAINS` for T-Head SoCs,
allowing the power domain driver for these components to be compiled and
integrated. This ensures proper power management and energy efficiency
on T-Head platforms.

By selecting `PM_GENERIC_DOMAINS`, we provide the necessary framework
for the power domain drivers to function correctly on RISC-V
architecture with T-Head SoCs.

Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
Reviewed-by: Drew Fustini <drew@pdp7.com>
Acked-by: Drew Fustini <drew@pdp7.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>