ARM: OMAP1: recalculate loops per jiffy after dpll1 reprogram

Otherwise timing is inaccurate, resulting in devices which depend on it,
like omap-keypad, broken.

Tested on Amstrad Delta.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
[tony@atomide.com: removed comment referencing a development branch]
Signed-off-by: Tony Lindgren <tony@atomide.com>