arm64: zynqmp: Add pinctrl emmc description to SM-K26

Production SOM has emmc on it and make sense to describe pin description to
be able use EMMC if it is not configured via psu_init.
(Still some regs are not handled but this is one step in that direction)

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/f61c16e2fd7c91c2be6d6b67c902037580dbd364.1683034376.git.michal.simek@amd.com