net: zynq: Fix MDC setting for zynq

Based on spec:
"MDC must not exceed 2.5 MHz (MDC is only active during MDIO read and
write operations)"
Zynq is running on 111MHz. Current setting is 32 which is 111/32=3.47
which is above of 2.5MHz.
Using 48 divider will give us correct setting according spec
(111/48=2.31).

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

drivers/net/zynq_gem.c

@@ -58,7 +58,7 @@
 #define ZYNQ_GEM_NWCFG_SPEED1000	0x000000400 /* 1Gbps operation */
 #define ZYNQ_GEM_NWCFG_FDEN		0x000000002 /* Full Duplex mode */
 #define ZYNQ_GEM_NWCFG_FSREM		0x000020000 /* FCS removal */
-#define ZYNQ_GEM_NWCFG_MDCCLKDIV	0x000080000 /* Div pclk by 32, 80MHz */
+#define ZYNQ_GEM_NWCFG_MDCCLKDIV	0x0000c0000 /* Div pclk by 48, max 120MHz */
 
 #ifdef CONFIG_ARM64
 # define ZYNQ_GEM_DBUS_WIDTH	(1 << 21) /* 64 bit bus */