[media] s5p-jpeg: Remove some unused functions

Removes some functions that are not used anywhere:
s5p_jpeg_input_raw_y16() s5p_jpeg_timer_disable() s5p_jpeg_timer_enable().

This was partially found by using a static code analysis program called
cppcheck.

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>