x86/kexec: Do not reserve EFI setup_data in the kexec e820 table

x86/kexec: Do not reserve EFI setup_data in the kexec e820 table

The e820 table for the kexec kernel unconditionally marks setup_data as
reserved because the second kernel can reuse setup_data passed by the
1st kernel's boot loader, for example SETUP_PCI marked regions like PCI
BIOS, etc.

SETUP_EFI types, however, are used by kexec itself to enable EFI in the
2nd kernel. Thus, it is pointless to add this type of setup_data to the
kexec e820 table as reserved.

IOW, what happens is this:

  -  1st physical boot: no SETUP_EFI.

  - kexec loads a new kernel and prepares a SETUP_EFI setup_data blob, then
  reboots the machine.

  - 2nd kernel sees SETUP_EFI, reserves it both in the e820 and in the
  kexec e820 table.

  - If another kexec load is executed, it prepares a new SETUP_EFI blob and
  then reboots the machine into the new kernel.

  5. The 3rd kexec-ed kernel has two SETUP_EFI ranges reserved. And so on...

Thus skip SETUP_EFI while reserving setup_data in the e820_table_kexec
table because it is not needed.

 [ bp: Heavily massage commit message, shorten line and improve comment. ]

Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200212110424.GA2938@dhcp-128-65.nay.redhat.com