[PATCH] Add mmap in libbsd

[Vijay Kumar Banerjee]

Hello,

The following patch adds d_mmap_t to the cdevsw through a wrapper
devfs_imfs_mmap to connect the RTEMS mmap to the respective driver
mmap in the libbsd drivers. 

This patch DOES NOT have a devfs test included and hence is NOT
mergeable as of now. This is a preview patch and the intention is
to get reviews on the patch and to let Nil's project go on without
having to wait for the full patch. I will soon be adding a test and
will post the v2 of the patch which will be mergeable.

Thanks,
Vijay