Fix further conversion errors found while testing the converted keymaps.

MFC after:	3 days
Fix conversion errors leading to malformed keymap files.

MFC after:	3 days
Add arch-specific macro SFBUF_PHYS_DMAP(), which should translate the
physical address of the page to direct map address, in case
SFBUF_OPTIONAL_DIRECT_MAP returns true.  The case of PowerPC AIM
64bit, where the page physical address is identical to the direct map
address, is accidental.

Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
Increase max number of physical segments on amd64 to 63.

Eventually, the vmd_segs of the struct vm_domain should become bitset
instead of long, to allow arbitrary compile-time selected maximum.

Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Correct the test for condition to suspend UFS filesystem during
unmount.  There is no need to suspend read-only filesystem, while we
need suspension on modificable mount point.

Reported by:	rwatson
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Do not busy the UFS mount point inside VOP_RENAME().  The
kern_renameat() already starts write on the mp, which prevents
parallel unmount from proceed.  Busying mp after vn_start_write()
deadlocks the unmount.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week