Rename CONFIG_SYS_TEXT_BASE to CONFIG_TEXT_BASE

The current name is inconsistent with SPL which uses CONFIG_SPL_TEXT_BASE
and this makes it imposible to use CONFIG_VAL().

Rename it to resolve this problem.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/rpi_3_b_plus_defconfig b/configs/rpi_3_b_plus_defconfig
index e112fca..8fd74fc 100644
--- a/configs/rpi_3_b_plus_defconfig
+++ b/configs/rpi_3_b_plus_defconfig
@@ -1,7 +1,7 @@
 CONFIG_ARM=y
 CONFIG_ARCH_CPU_INIT=y
 CONFIG_ARCH_BCM283X=y
-CONFIG_SYS_TEXT_BASE=0x00080000
+CONFIG_TEXT_BASE=0x00080000
 CONFIG_TARGET_RPI_3=y
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ENV_SIZE=0x4000