mfd: cgbc-core: Cleanup signedness in cgbc_session_request()

This doesn't affect how the code works because there are some implicit
casts, but the "ret" variable is used to hold negative error codes so
it should be type int.

Declare it as "int" instead of "unsigned int".

Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/9e812dfa-e216-4e40-bbf0-d0b63b110bb0@stanley.mountain


Signed-off-by: Lee Jones <lee@kernel.org>