[media] exynos-gsc: remove an always false condition

As reported by smatch:
drivers/media/platform/exynos-gsc/gsc-core.c:1073 gsc_probe() warn: impossible condition '(gsc->id < 0) => (0-65535 < 0)'
drivers/media/platform/exynos-gsc/gsc-core.c: In function 'gsc_probe':
drivers/media/platform/exynos-gsc/gsc-core.c:1073:51: warning: comparison is always false due to limited range of data type [-Wtype-limits]
  if (gsc->id >= drv_data->num_entities || gsc->id < 0) {
                                                   ^

gsc->id is an u16, so it can never be a negative number. So,
remove the always false condition.

Fixes: c1ac0571

 "[media] exynos-gsc: remove non-device-tree init code"
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>