sunxi: move CONFIG_SYS_TEXT_BASE out of defconfigs

Commit 278b90ce78 ("configs: Migrate CONFIG_SYS_TEXT_BASE") made
CONFIG_SYS_TEXT_BASE a proper Kconfig variable, with the consequence
of moving the common definition shared by almost every sunxi board
into 123 individual defconfig files. But the U-Boot start address
for Allwinner boards is a platform decision which has been around for
ages, so defining it in each *board* config file seems a bit over the
top.
Define the standard values (160MB into DRAM for most SoCs, with two
SoC exceptions) if ARCH_SUNXI is selected, and delete the lines from
the individual defconfigs.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>

configs/Auxtek-T004_defconfig

@@ -1,6 +1,5 @@
 CONFIG_ARM=y
 CONFIG_ARCH_SUNXI=y
-CONFIG_SYS_TEXT_BASE=0x4a000000
 CONFIG_MACH_SUN5I=y
 CONFIG_DRAM_CLK=432
 CONFIG_USB1_VBUS_PIN="PG13"