[media] ths8200: fix two compiler warnings

[media] ths8200: fix two compiler warnings

drivers/media/i2c/ths8200.c: In function ‘ths8200_g_register’:
drivers/media/i2c/ths8200.c:121:21: warning: unused variable ‘client’ [-Wunused-variable]
drivers/media/i2c/ths8200.c: In function ‘ths8200_s_register’:
drivers/media/i2c/ths8200.c:132:21: warning: unused variable ‘client’ [-Wunused-variable]

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Prabhakar Lad <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>