util: Use reg_belongs_to_class instead of BITSET_TEST

This shouldn't be a functional change since reg_belongs_to_class is just a
wrapper around BITSET_TEST.  It just makes the code a little easier to
read.

Signed-off-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
1 file changed