Don't open code the min/max delta logic. Use the generic
version instead. Also expand the number of bits we can handle
because there isn't anything that says we can't handle all 32
bits.

Before:
 max_delta_ns:   122880426391799
 min_delta_ns:   122070
 mult:           140737
 shift:          32

After:
 max_delta_ns:   131071523464981
 min_delta_ns:   122069
 mult:           70369
 shift:          31
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: David Brown <davidb@codeaurora.org>