ARM: OMAP: clock: Nuke plat/clock.c & reuse struct clk as clk_hw_omap

plat/clock.c which has most of usecounting/locking infrastructure will
be used only for OMAP1 until that is moved to use COMMON clk.

reuse most of what plat/clock.h has while we move to common clk, and
move most of what 'struct clk' was as 'struct clk_hw_omap' which
will then be used to define platform specific parameters.
All usecounting/locking related variables from 'struct clk' are
dropped as they will not be used with 'struct clk_hw_omap'.

Based on the original changes from Mike Turquette.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Mike Turquette <mturquette@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>