miiphy: miiphyutil.c: fix compile warning

Fix warning introduced while recent PHY Lib changes:

miiphyutil.c: In function 'miiphy_read':
miiphyutil.c:304: warning: comparison is always false due to limited range of data type

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Andy Fleming <afleming@freescale.com>
1 file changed