Remove some clutter from omap2_dpll_round_rate().

linux-omap source commit is 4625dceb8583c02a6d67ededc9f6a8347b6b8cb7.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>