[media] i2c: tc358743: remove useless variable assignment in tc358743_isr

Remove useless variable assignment in function tc358743_isr().

The value stored in variable _intstatus_ at line 1299 is
overwritten at line 1302, just before it can be used.

Addresses-Coverity-ID: 1397678

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>