OMAP4: clock data: Remove usb_host_fs clkdev with NULL dev

usb_host_fs_fck does have a clkdev mapping with "usbhs-omap.0"
and "fs_fck" alias used by the driver.
The entry with NULL dev is thus not needed anymore.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Felipe Balbi <balbi@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>