OMAP2/3 clock: use clk->prcm_mod for all struct clk register addressing

Use the clk->prcm_mod field for all register addresses in struct clk.
Remove all usage of the *_REGADDR() and *_OFFSET() macros from the
clock tree.  This eliminates a set of (__force void __iomem *) casts
and removes all of the OMAP2xxx register address rewriting.  Shrink
the width of the enable_reg/clksel_reg registers to 16 bits, saving 4
bytes per struct clk.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>