net: stmmac: remove unnecessary pci_enable_msi() call

The commit d2a029bd ("stmmac: pci: add MSI support for Intel Quark
X1000") introduced a pci_enable_msi() call in stmmac_pci.c.

With the commit 58da0cfa ("net: stmmac: create dwmac-intel.c to
contain all Intel platform"), Intel Quark platform related codes
have been moved to the newly created driver.

Removing this unnecessary pci_enable_msi() call as there are no other
devices that uses stmmac-pci and need MSI to be enabled.

Signed-off-by: Wong Vee Khee <vee.khee.wong@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>