media: smiapp: Rename update_mode as pll_blanking_update

Rename the confusingly named smiapp_update_mode() function as
smiapp_pll_blanking_update(). The function is used to calculate new PLL
and blanking configuration after binning or scaling configuration has been
changed.

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