fsl/usb: Limit phy_type comparison to first four characters

fsl/usb: Limit phy_type comparison to first four characters

Use first four characters for phy_type comparison. Strcmp() should not
be used to check the phy_type string which maybe parsed by hwconfig_subarg().
Hwconfig_subarg() returns part of hwconfig string starting from
phy_type value till the end of the string. Since phy_type could be
either "utmi" or "ulpi", strncmp() should be used so that a comparison
of "utmi;fsl_ddr:bank_intlv=auto" with "utmi" will succeed.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Nikhil Badola <nikhil.badola@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>