config: ti_omap5_common: Palmas power support in SPL

Palmas power support is required for OMAP5 devices such as the OMAP5 uEVM, that
need to e.g. enable MMC power at SPL stage.

This is especially important when booting from a peripheral (such as USB, UART),
where the bootrom will not enable power for the MMC device that will hold the
main U-Boot.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Tom Rini <trini@konsulko.com>