LinuxKPI: Use macro for implementation of some dma_map_* functions

This allows to remove unimplemented attrs parameter which type differs
between Linux kernel versions and to compile both drm-kmod and ofed
callers unmodified.
Also convert it to 'unsigned long' type to match modern Linuxes.

Reviewed by: hselasky
Differential revision: https://reviews.freebsd.org/D30932