x86: Remove more unmodified io_apic_ops

io_apic_ops.init() is either NULL, if IO-APIC support is disabled at
compile time or native_io_apic_init_mappings(). No point to have that
as we can achieve the same thing with an empty inline.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --cc arch/x86/include/asm/io_apic.h
Simple merge

diff --cc arch/x86/include/asm/x86_init.h
Simple merge

diff --cc arch/x86/kernel/apic/io_apic.c
Simple merge

diff --cc arch/x86/kernel/setup.c
Simple merge

diff --cc arch/x86/kernel/x86_init.c
Simple merge