[media] si4713: Bug fix for si4713_tx_tune_power() method in the i2c driver

In the si4713_tx_tune_power() method, the args array element 'power'
can take values between SI4713_MIN_POWER and SI4713_MAX_POWER. power = 0
is also valid. All the values (0 > power < SI4713_MIN_POWER) are illegal
and hence are all mapped to SI4713_MIN_POWER.

Signed-off-by: Dinesh Ram <dinesh.ram@cern.ch>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Eduardo Valentin <edubezval@gmail.com>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>