ARM: zynq: Define sys prompt for all Zynq boards

Define CONFIG_SYS_PROMPT for all Zynq boards

It was removed by:
"kconfig: add config option for shell prompt"
(sha1: 181bd9dc61d2da88b78f1c1138a685dae39354d6)

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 75d6c55..b0fa661 100644
--- a/configs/zynq_zc770_xm012_defconfig
+++ b/configs/zynq_zc770_xm012_defconfig
@@ -7,6 +7,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_FIT_SIGNATURE=y
 CONFIG_SYS_EXTRA_OPTIONS="ZC770_XM012"
+CONFIG_SYS_PROMPT="Zynq> "
 CONFIG_CMD_GPIO=y
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_NET_RANDOM_ETHADDR=y