usb: host: make ehci_fsl_overrides const and __initconst

Make this structure const as it is not modified. And replace __initdata
with __initconst to avoid section conflict error.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>