zynq: defconfig: Remove unnecessary board specific config files

Remove unnecessary board specifc config files for
zynq boards(microzed, picozed, ZC770(all), zed) and point
to zynq common config file.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/zynq_zc770_xm012_defconfig b/configs/zynq_zc770_xm012_defconfig
index a8cfeb8..b3a75a6 100644
--- a/configs/zynq_zc770_xm012_defconfig
+++ b/configs/zynq_zc770_xm012_defconfig
@@ -1,5 +1,5 @@
 CONFIG_ARM=y
-CONFIG_SYS_CONFIG_NAME="zynq_zc770"
+CONFIG_SYS_CONFIG_NAME="zynq-common"
 CONFIG_ARCH_ZYNQ=y
 CONFIG_DEFAULT_DEVICE_TREE="zynq-zc770-xm012"
 CONFIG_SPL=y