Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r243025: boot: use packed attribute for edd_params* structures

MFC 226748:
- Add a new header for the x86 boot code that defines various structures
and constants related to the BIOS Enhanced Disk Drive Specification.
- Use this header instead of magic numbers and various duplicate structure
definitions for doing I/O.
- Use an actual structure for the request to fetch drive parameters in
drvsize() rather than a gross hack of a char array with some magic
size. While here, change drvsize() to only pass the 1.1 version of
the structure and not request device path information. If we want
device path information you have to set the length of the device
path information as an input (along with probably checking the actual
EDD version to see which size one should use as the device path
information is variable-length). This fixes data smashing problems
from passing an EDD 3 structure to BIOSes supporting EDD 4.

Approved by: re (kib)

- Add a new header for the x86 boot code that defines various structures
and constants related to the BIOS Enhanced Disk Drive Specification.
- Use this header instead of magic numbers and various duplicate structure
definitions for doing I/O.
- Use an actual structure for the request to fetch drive parameters in
drvsize() rather than a gross hack of a char array with some magic
size. While here, change drvsize() to only pass the 1.1 version of
the structure and not request device path information. If we want
device path information you have to set the length of the device
path information as an input (along with probably checking the actual
EDD version to see which size one should use as the device path
information is variable-length). This fixes data smashing problems
from passing an EDD 3 structure to BIOSes supporting EDD 4.

Reviewed by: avg
Tested by: Dennis Koegel dk neveragain.de
MFC after: 1 week