[CORE] Add mult and shift calculator for both clksource and chip.

This patch adds function vmm_clocks_calc_mult_shift which, as the
name suggests, calculate both the shift and the multiplication factor
based on clock frequency and guaranteed runtime conversion range.

This has been taken as is from Linux's clocks_calc_mult_shift.

Signed-off-by: Anup Patel <anup@brainfault.org>