sunxi: Enable THUMB build for the U-Boot binary

We start to get to the limit of our main U-Boot binary size (with some
boards even crossing it). Enable its build using thumb2 to get some extra
room.

Suggested-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/Kconfig

@@ -698,6 +698,7 @@ config ARCH_SUNXI
 	select SPL_SYS_MALLOC_SIMPLE if SPL
 	select SYS_NS16550
 	select SPL_SYS_THUMB_BUILD if !ARM64
+	select SYS_THUMB_BUILD if !ARM64
 	select USB if DISTRO_DEFAULTS
 	select USB_STORAGE if DISTRO_DEFAULTS
 	select USB_KEYBOARD if DISTRO_DEFAULTS