media: ov6650: Simplify clock divisor calculation

As appears from an analysis of to_clkrc() helper code after its
pclk_limit argument has been dropped, its result no longer depends on
another argument - pclk_max.  Moreover, assuming that a constant value
of FRAME_RATE_MAX is always used as a denominator of the only
significant argument left - a struct v4l2_fract, the result in fact
depends only on the numerator value of that argument.  As a further
consequence, it no longer makes sense to recalculate frame intervals by
converting them forth and back with a GET_CLKRC_DIV(to_clkrc(tpf))
construct.

Drop use of GET_CLKRC_DIV() on results of to_clkrc() where possible -
use the frame interval value directly.  Furthermore, replace the
to_clkrc() helper function with a simple macro and update its users to
always use FRAME_RATE_MAX as frame interval denominator and pass only
its numerator as an argument.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>