arm: zynq: zybo z7: fix MIO init issue

The board has two push button connected to MIO pins
50 and 51, which have a pull-down resistor and are
connected to 1.8V when pressed.

These two pins are wrongly initialized with internal
pull-up enabled so they are reported as 1 all the time
with no change when pressed.

Disable the internal pull-up to fix the issue.

Signed-off-by: Milan Obuch <u-boot@dino.sk>
Signed-off-by: Luis Araneda <luaraneda@gmail.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/zynq/zynq-zybo-z7/ps7_init_gpl.c b/board/xilinx/zynq/zynq-zybo-z7/ps7_init_gpl.c
index 7c6bc9f..a376ba5 100644
--- a/board/xilinx/zynq/zynq-zybo-z7/ps7_init_gpl.c
+++ b/board/xilinx/zynq/zynq-zybo-z7/ps7_init_gpl.c
@@ -219,8 +219,8 @@
 	EMIT_MASKWRITE(0xF80007BC, 0x00003F01U, 0x00001201U),
 	EMIT_MASKWRITE(0xF80007C0, 0x00003FFFU, 0x000012E0U),
 	EMIT_MASKWRITE(0xF80007C4, 0x00003FFFU, 0x000012E1U),
-	EMIT_MASKWRITE(0xF80007C8, 0x00003FFFU, 0x00001200U),
-	EMIT_MASKWRITE(0xF80007CC, 0x00003FFFU, 0x00001200U),
+	EMIT_MASKWRITE(0xF80007C8, 0x00003FFFU, 0x00000200U),
+	EMIT_MASKWRITE(0xF80007CC, 0x00003FFFU, 0x00000200U),
 	EMIT_MASKWRITE(0xF80007D0, 0x00003FFFU, 0x00001280U),
 	EMIT_MASKWRITE(0xF80007D4, 0x00003FFFU, 0x00001280U),
 	EMIT_MASKWRITE(0xF8000830, 0x003F003FU, 0x002F0037U),