Refactor function has_cap in order to avoid returning integer
values, when instead it should return booleans.

This code was detected with the help of Coccinelle.
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: N"Lee, Chun-Yi" <jlee@suse.com>
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>