gpio: fix incorrect depends on for SPL_GPIO_HOG

Since commit 83061dbd ("Rename GPIO_SUPPORT to GPIO"),
SPL_GPIO_SUPPORT has been renamed to SPL_GPIO, meaning that SPL_GPIO_HOG
can never be enabled.

Let's fix this by using the proper name for the Kconfig option.

Fixes: 1d99e673 ("gpio: Enable hogging support in SPL")
Cc: Quentin Schulz <foss+uboot@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>