Impact: cleanup, reduce kernel size a bit, avoid sparse warnings

Fixes sparse warnings:
arch/x86/kernel/genx2apic_phys.c:164:6: warning: symbol 'x2apic_send_IPI_self' was not declared. Should it be static?
arch/x86/kernel/genx2apic_phys.c:169:6: warning: symbol 'init_x2apic_ldr' was not declared. Should it be static?
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>