OMAP4: clock data: Fix max mult and div for USB DPLL

The DPLL USB can generate higher speed (x2) than the regular ones.
The max multiplication value is then twice the previous value.

Fix both max_mult and max_div with that correct values.

Change the max_div variable type to u16 to allow storing up to 256.

Replace as well the define with the value to avoid
unneeded indirection and provide a better readability.

Remove the defines that become useless.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>