[media] s5c73m3/s5k5baf/s5k6aa: fix compiler warnings

[media] s5c73m3/s5k5baf/s5k6aa: fix compiler warnings

Fix these compiler warnings that appeared after switching to gcc-5.1.0:

drivers/media/i2c/s5k5baf.c: In function 's5k5baf_set_power':
drivers/media/i2c/s5k5baf.c:1057:10: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
  if (!on != state->power)
          ^
drivers/media/i2c/s5k6aa.c: In function 's5k6aa_set_power':
drivers/media/i2c/s5k6aa.c:878:10: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
  if (!on == s5k6aa->power) {
          ^
drivers/media/i2c/s5c73m3/s5c73m3-core.c: In function 's5c73m3_oif_set_power':
drivers/media/i2c/s5c73m3/s5c73m3-core.c:1456:17: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
  } else if (!on == state->power) {
                 ^

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>