MXC : update i.MX21 clock support for USB host.
MXC : update i.MX21 clock support for USB host.

* Use correct clkdev style usb clock name
* Implement rate setting for USB clock
* Introduce _clk_generic_round_rate to factorize the (now 3) uses of rounding code.

Signed-off-by: Martin Fuzzey <b2501a40abc3919adb877696d4c7db7ff9886710@gmail.com>
Signed-off-by: Sascha Hauer <c00cbc2b736c26791a3822db86f8796fe9efff67@pengutronix.de>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas