media: atomisp: make hive_int8 explictly signed

media: atomisp: make hive_int8 explictly signed

The current definition of hive_int8 is a naked char, without any sign
specifier. This is incorrect on platforms such as arm, where char is
unsigned. Fortunately nothing in the kernel actually uses a hive_int8
type, but in case it gets used later rather than removed, this makes it
explicitly signed.

Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>