media: tvp5150: split reset/enable routine

To trigger standard autodetection only the reset part of the routine
is necessary during probe(). Split this out to make it callable on its own.

[m.felsch@pengutronix.de: adapt commit message]
[m.felsch@pengutronix.de: add tvp5150_enable() to tvp5150_s_stream()]
[m.chehab@samsung.com: fix a compilation breakage]
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>