memory: omap-gpmc: Make OMAP_GPMC config visible and selectable

memory: omap-gpmc: Make OMAP_GPMC config visible and selectable

So far for armv7 TI platforms, GPMC was being selected by
arch/arm/mach-* architecture Kconfig files.

For K3 platforms, GPMC is no longer required for basic boot and cannot
be always enabled by default by mach- Kconfig.

We need a way for user (or board defconfig) to enable it if required so
make OMAP_GPMC Kconfig option always visible.

Drop COMPILE_TEST as build fails if IRQ_DOMAIN is not enabled.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Link: https://lore.kernel.org/r/20220426082611.24427-2-rogerq@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>