media: qcom: camss: Use a macro to specify the initial buffer count

media: qcom: camss: Use a macro to specify the initial buffer count

Replace the hardcoded buffer count value with a macro to enable
operating on these buffers elsewhere in the CAMSS driver based on this
count. Some of the hardware architectures require deferring the AUP and
REG update until after the CSID configuration and this macro is expected
to be useful in such scenarios.

Signed-off-by: Hangxiang Ma <hangxiang.ma@oss.qualcomm.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Bryan O'Donoghue <bod@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>