media: qcom: camss: Rename camss-vfe-780.c to camss-vfe-gen3.c

media: qcom: camss: Rename camss-vfe-780.c to camss-vfe-gen3.c

Rename the file camss-vfe-780.c to camss-vfe-gen3.c to enable
reuse of VFE logic across multiple SoCs.

The lemans(sa8775p) SoC includes VFE 690, which is very similar
to VFE 780, with only minor differences in register bitfields.
Rename prepares the codebase for supporting additional SoCs
without duplicating VFE logic.

Signed-off-by: Vikram Sharma <quic_vikramsa@quicinc.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>