Use the SMAP data from the loader if it is provided instead of using

Use the SMAP data from the loader if it is provided instead of using
virtual 86 mode to query the BIOS directly.  This is needed for certain
HP machines whose BIOS only provide an SMAP when invoked from real mode.
On such machines the loader will be able to query the SMAP successfully
due to the recent BTX changes, but the kernel will not.

One thing I'm not sure of is if we can skip the INT 12h probe altogether
if we have the SMAP from the loader as it seems that we do the INT 12h
probe to setup enough state so we can use vm86 to call the BIOS.

MFC after:	1 week