Revert "x86/microcode: Rip out the OLD_INTERFACE"

Intel inclusion
category: feature
feature: Backport Intel In Field Scan(IFS) multi-blob images support
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I6L337


CVE: N/A
Reference: N/A

Intel-SIG: Revert commit 05a2ea3f ("x86/microcode: Rip out the
OLD_INTERFACE")

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

This reverts commit 05a2ea3f.

This revert is to recover old microcode interface /dev/cpu/microcode.

Signed-off-by: Aichun Shi <aichun.shi@intel.com>