memory: omap-gpmc: remove unneeded asm/mach-types.h inclusion

The driver does not use macros from asm/mach-types.h (neither MACH_TYPE
nor machine_is_xxx()).  Removal of this include allows compile testing
on non-ARM architectures which lack this header.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200724074038.5597-2-krzk@kernel.org

drivers/memory/omap-gpmc.c

@@ -33,8 +33,6 @@
 
 #include <linux/platform_data/mtd-nand-omap2.h>
 
-#include <asm/mach-types.h>
-
 #define	DEVICE_NAME		"omap-gpmc"
 
 /* GPMC register offsets */