[media] ov2659: get rid of unused values

Why to store the chosed values for prediv, postdiv and mult if
those won't be used?

drivers/media/i2c/ov2659.c: In function 'ov2659_pll_calc_params':
drivers/media/i2c/ov2659.c:912:35: warning: variable 's_mult' set but not used [-Wunused-but-set-variable]
  u32 s_prediv = 1, s_postdiv = 1, s_mult = 1;
                                   ^
drivers/media/i2c/ov2659.c:912:20: warning: variable 's_postdiv' set but not used [-Wunused-but-set-variable]
  u32 s_prediv = 1, s_postdiv = 1, s_mult = 1;
                    ^
drivers/media/i2c/ov2659.c:912:6: warning: variable 's_prediv' set but not used [-Wunused-but-set-variable]
  u32 s_prediv = 1, s_postdiv = 1, s_mult = 1;
      ^

This is likely some leftover from some past change.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>