x86/microcode/AMD: Remove unused save_microcode_in_initrd_amd() declarations

Commit

  a7939f01 ("x86/microcode/amd: Cache builtin/initrd microcode early")

renamed it to save_microcode_in_initrd() and made it static. Zap the
forgotten declarations.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20250211163648.30531-3-bp@kernel.org