x86/apic: Fix a comment in init_apic_mappings()

commit c0104d38

 ("x86, apic: Unify identical register_lapic_address()
functions") renames acpi_register_lapic_address to register_lapic_address.

But acpi_register_lapic_address remains in a comment, and renaming it to
register_lapic_address is not suitable for this comment.

Remove acpi_register_lapic_address and rewrite the comment.

[ tglx: LAPIC address can be registered either by ACPI/MADT or MP info ]

Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/1488805690-5055-1-git-send-email-douly.fnst@cn.fujitsu.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>