sunxi: Remove CONFIG_TARGET_FOO for sun4i, sun6i and sun8i boards

CONFIG_TARGET_FOO is only used in board/sunxi/Makefile to select the
dram config for sun5i and sun7i boards and in board/sunxi/gmac.c for some
special handling of the bananapi/bananapro (both sun7i), iow it is not used
at all on any sun4i, sun6i and sun8i boards so lets get rid of it there.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/configs/MSI_Primo81_defconfig b/configs/MSI_Primo81_defconfig
index b4b0f6d..140f864 100644
--- a/configs/MSI_Primo81_defconfig
+++ b/configs/MSI_Primo81_defconfig
@@ -1,3 +1,12 @@
+# The MSI Primo81 is an A31s based tablet, with 1G RAM, 16G NAND,
+# 1024x768 IPS LCD display, mono speaker, 0.3 MP front camera, 2.0 MP
+# rear camera, 3500 mAh battery, gt911 touchscreen, mma8452 accelerometer
+# and rtl8188etv usb wifi. Has "power", "volume+" and "volume-" buttons
+# (both volume buttons are also connected to the UBOOT_SEL pin). The
+# external connectors are represented by MicroSD slot, MiniHDMI, MicroUSB
+# OTG and 3.5mm headphone jack. More details are available at
+#     http://linux-sunxi.org/MSI_Primo81
+
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS=""
 CONFIG_FDTFILE="sun6i-a31s-primo81.dtb"
@@ -5,7 +14,6 @@
 +S:CONFIG_ARM=y
 +S:CONFIG_ARCH_SUNXI=y
 +S:CONFIG_MACH_SUN6I=y
-+S:CONFIG_TARGET_MSI_PRIMO81=y
 +S:CONFIG_DRAM_CLK=360
 +S:CONFIG_DRAM_ZQ=122
 # Wifi power