intel/decoder: Take a bit offset in gen_print_group

intel/decoder: Take a bit offset in gen_print_group

Previously, if a group was nested in another group such that it didn't
start on a dword boundary, we would decode it as if it started at the
start of its first dword.  This changes things to work even more in
terms of bits so that we can properly decode these structs.  This
affects MOCS, attribute swizzles, and several other things.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>