gpio: nomadik: add #include <linux/slab.h>

Add linux/slab.h header include for GFP flags.
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://lore.kernel.org/r/20240228-mbly-gpio-v2-14-3ba757474006@bootlin.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-nomadik.c

@@ -23,6 +23,7 @@
 #include <linux/platform_device.h>
 #include <linux/reset.h>
 #include <linux/seq_file.h>
+#include <linux/slab.h>
 #include <linux/types.h>
 
 #include <linux/gpio/gpio-nomadik.h>