x86/boot/32: Restructure mk_early_pgtbl_32()

mainline inclusion
from mainline-v6.7-rc1
commit 69ba866db281c768d5ecca909361ea4c4e71d57e
category: feature
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I8XRMW


CVE: NA

--------------------------------

Prepare it for adding a temporary initrd mapping by splitting out the
actual map loop.

No functional change.

Intel-SIG: commit 69ba866db281 x86/boot/32: Restructure mk_early_pgtbl_32().
Microcode restructuring backport.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231017211722.175910753@linutronix.de


[ Aubrey Li: amend commit log ]
Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>