MFC r270179:

  Add missing libraries to DPADD; sort DPADD so DPADD and LDADD match up

  This fixes "make checkdpadd"

  Approved by: jmmv (mentor)
  Phabric: D630
  PR: 192765
MFC r263826: Update EFI framebuffer handoff from loader

Sponsored by:	The FreeBSD Foundation
Revert r268372 - enable vt_efifb vt(4) driver again.

It was disabled as some parts of UEFI support had not yet been merged to
stable/10.

Sponsored by:	The FreeBSD Foundation
MFC r268624 by nwhitehorn:

  On my Lenovo laptop, the firmware maps the EFI framebuffer with MTRRs
  set to uncacheable. This leads to execrable console performance. Once
  PMAP is up, remap the framebuffer as write-combining. This reduces
  boot time on my laptop by 60% when booting with EFI.
MFC part of r267973: remove redundant "" assignment for string in BSS.

Sponsored by:	The FreeBSD Foundation
MFC r268771, r268796 by nwhitehorn:

r268771:
  Allow console drivers active from early boot to be used with
  xf86-video-scfb, rather than only drivers attached later on. This
  involves a small amount of code duplication with dev/fb/fbd.c, which
  will fixed later on.

  Also improve performance of vt_blank() by making it not read from the
  framebuffer unnecessarily.

r268796:
  Fix embarassing typos I made.

Sponsored by:	The FreeBSD Foundation
MFC r268772 by nwhitehorn:

  Allow efifb to be used with xf86-video-scfb. This is important for EFI
  systems without either a CSM or real graphics drivers, such as my
  Lenovo Haswell laptop.

  This provides working X with the small complication of a console
  cursor permanently overlaid on the upper-left corner of the screen
  that will be dealt with later.

  Also remove some redundant screen clearing.

Sponsored by:	The FreeBSD Foundation
MFC r269185 by ray@: Remove unused macro VT_CONSDEV_DECLARE.

Sponsored by:	The FreeBSD Foundation
MFC r269186 by ray@: Remove useless debug string.

  Fix indent.

Sponsored by:	The FreeBSD Foundation
MFC automatic vt(4) selection for UEFI boot

r268158: Prefer vt(4) for UEFI boot

  The UEFI framebuffer driver vt_efifb requires vt(4), so add a
  mechanism for the startup routine to set the preferred console.
  This change is ugly because console init happens very early in the
  boot, making a cleaner interface difficult.  This change is intended
  only to facilitate the sc(4) / vt(4) transition, and can be reverted
  once vt(4) is the default.

r268160: Fix typos in VTY constant names from r268158

r268982: Don't pass null kmdp to preload_search_info

  On Xen PVH guests kmdp == NULL.

Sponsored by:	The FreeBSD Foundation