omap3: Define maximum U-Boot size in Kconfig instead of defconfigs

The maximum U-Boot size was defined to the same value in each OMAP3
board defconfig. Move the common definition to the Kconfig option
declaration instead.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Tom Rini <trini@konsulko.com>
Tested-by: Derald D. Woods <woods.technical@gmail.com>
diff --git a/Kconfig b/Kconfig
index 70c26b4..69e8b17 100644
--- a/Kconfig
+++ b/Kconfig
@@ -620,6 +620,7 @@
 config SYS_MONITOR_LEN
 	int "Maximum size in bytes reserved for U-Boot in memory"
 	default 1048576 if X86
+	default 262144 if OMAP34XX
 	default 786432 if ARCH_SUNXI
 	default 0
 	help