configs: omap35_logic_somlv: Fix MMC booting

A previous patch had removed the GPIO nodes from being built
into the SPL Device tree, but CONFIG_SPL_GPIO_SUPPORT remained
which makes the MMC card detect fail and the board does not boot.
Fix this by disabling CONFIG_SPL_GPIO_SUPPORT.

Fixes: 6f1efe81 ("configs: omap3/35_logic and omap3/35_logic_somlv: Reduce SPL size")
Signed-off-by: Adam Ford <aford173@gmail.com>