[PATCH -next] net: phy: test the right variable in phy_write_mmd()

[Dan Carpenter]

This is a copy and paste buglet.  We meant to test for ->write_mmd but
we test for ->read_mmd.

Fixes: 1ee6b9bc6206 ("net: phy: make phy_(read|write)_mmd() generic MMD 
accessors")
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
index 357a4d0d7641..6739b738bbaf 100644
--- a/drivers/net/phy/phy-core.c
+++ b/drivers/net/phy/phy-core.c
@@ -76,7 +76,7 @@ int phy_write_mmd(struct phy_device *phydev, int devad, u32 
regnum, u16 val)
        if (regnum > (u16)~0 || devad > 32)
                return -EINVAL;
 
-       if (phydev->drv->read_mmd) {
+       if (phydev->drv->write_mmd) {
                ret = phydev->drv->write_mmd(phydev, devad, regnum, val);
        } else if (phydev->is_c45) {
                u32 addr = MII_ADDR_C45 | (devad << 16) | (regnum & 0xffff);