ARM: omap3: Implement dpll5 (HSUSB clk) workaround for OMAP36xx/AM/DM37xx according to errata sprz318e.

In chapter 'Advisory 2.1 USB Host Clock Drift Causes USB Spec Non-compliance in Certain Configurations' of the TI Errata it is recommended to use certain div/mult values for the DPLL5 clock setup.
So far u-boot used the old 34xx values, so I added the errata recommended values specificly for 36xx init only.
Also, the FSEL registers exist no longer, so removed them from init.

Tested this on a AM3703 board with 19.2MHz oscillator, which previously couldnt lock the dpll5 (kernel complained). As a consequence the EHCI USB port wasnt usable in U-Boot and kernel. With this patch, kernel panics disappear and USB working fine in u-boot and kernel.

Signed-off-by: Andreas Naumann <anaumann@ultratronik.de>
[trini: Add extern to <asm/arch-omap3/clock.h>
Signed-off-by: Tom Rini <trini@ti.com>