[ARM] OMAP2/3 clock: clean up mach-omap2/clock.c

This patch rolls up several cleanup patches.

1. Some unnecessarily verbose variable names are used in several clock.c
functions; clean these up per CodingStyle.

2. Remove omap2_get_clksel() and just use clk->clksel_reg and
clk->clksel_mask directly.

3. Get rid of void __iomem * usage in omap2_clksel_get_src_field.
Prepend the function name with an underscore to highlight that it is a
static function.

linux-omap source commits are 7fa95e007ea2f3c4d0ecd2779d809756e7775894,
af0ea23f1ee4a5bea3b026e38761b47089f9048a, and
91c0c979b47c44b08f80e4f8d4c990fb158d82c4.

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>