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/poleg_evb_defconfig b/configs/poleg_evb_defconfig
index 597a72e..914fc39 100644
--- a/configs/poleg_evb_defconfig
+++ b/configs/poleg_evb_defconfig
@@ -2,7 +2,7 @@
 CONFIG_ARCH_CPU_INIT=y
 CONFIG_SYS_L2_PL310=y
 CONFIG_ARCH_NPCM=y
-CONFIG_SYS_TEXT_BASE=0x8200
+CONFIG_TEXT_BASE=0x8200
 CONFIG_SYS_MALLOC_LEN=0x240000
 CONFIG_SYS_MALLOC_F_LEN=0x1000
 CONFIG_NR_DRAM_BANKS=2