rockchip: rk3188: follow THUMB_BUILD Kconfig migration

Commit 3a649407a4 ("arm: Migrate SYS_THUMB_BUILD to Kconfig, introduce
SPL_SYS_THUMB_BUILD") moved the THUMB_BUILD symbols from the header to
Kconfig symbols. With it still defined in the rk3188 header we end up
with a duplicate symbol and compile errors, so fix that.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Simon Glass <sjg@chromium.org>

include/configs/rk3188_common.h

@@ -18,7 +18,6 @@
 #define CONFIG_SYS_MAXARGS		16
 #define CONFIG_SYS_MALLOC_LEN		(32 << 20)
 #define CONFIG_SYS_CBSIZE		1024
-#define CONFIG_SYS_THUMB_BUILD
 
 #define CONFIG_SYS_TIMER_RATE		(24 * 1000 * 1000)
 #define CONFIG_SYS_TIMER_BASE		0x2000e000 /* TIMER3 */