configs: ti_armv7_keystone2: make SYS_TEXT_BASE configurable at build time

U-boot for general purpose KS2 devices is loaded to the beginning of the
internal memory (0x0c000000). Secure devices uses this memory and
CONFIG_SYS_TEXT_BASE has to be different for those devices.

This commit make this configurable at build time by giving
CONFIG_SYS_TEXT_BASE as a command line definition to make command.

Signed-off-by: Vitaly Andrianov <vitalya@ti.com>

include/configs/ti_armv7_keystone2.h

@@ -20,7 +20,9 @@
 /* SoC Configuration */
 #define CONFIG_ARCH_CPU_INIT
 #define CONFIG_SYS_ARCH_TIMER
+#ifndef CONFIG_SYS_TEXT_BASE
 #define CONFIG_SYS_TEXT_BASE		0x0c000000
+#endif
 #define CONFIG_SPL_TARGET		"u-boot-spi.gph"
 #define CONFIG_SYS_DCACHE_OFF