omap: i2c: make errata 1.153 workaround a separate function

This is to avoid insanely long lines and levels of indentation.

Signed-off-by: Alexander Shishkin <virtuoso@slind.org>
Cc: Nishant Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>