x86/boot/64: Move 5-level paging global variable assignments back

Commit 63bed966 ("x86/startup_64: Defer assignment of 5-level paging
global variables") moved assignment of 5-level global variables to later
in the boot in order to avoid having to use RIP relative addressing in
order to set them. However, when running with 5-level paging and SME
active (mem_encrypt=on), the variables are needed as part of the page
table setup needed to encrypt the kernel (using pgd_none(), p4d_offset(),
etc.). Since the variables haven't been set, the page table manipulation
is done as if 4-level paging is active, causing the system to crash on
boot.

While only a subset of the assignments that were moved need to be set
early, move all of the assignments back into check_la57_support() so that
these assignments aren't spread between two locations. Instead of just
reverting the fix, this uses the new RIP_REL_REF() macro when assigning
the variables.

Fixes: 63bed966

 ("x86/startup_64: Defer assignment of 5-level paging global variables")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/2ca419f4d0de719926fd82353f6751f717590a86.1711122067.git.thomas.lendacky@amd.com