x86/sev: Get rid of excessive use of defines

Remove all the defines of masks and bit positions for the GHCB MSR
protocol and use comments instead which correspond directly to the spec
so that following those can be a lot easier and straightforward with the
spec opened in parallel to the code.

Aligh vertically while at it.

No functional changes.

Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211110220731.2396491-6-brijesh.singh@amd.com