x86/apic: Unify interrupt mode setup for UP system

In UniProcessor kernel with UP_LATE_INIT=y, the interrupt delivery mode is
initialized in up_late_init().

Use the new unified apic_intr_mode_init() function and remove
APIC_init_uniprocessor().

Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: yinghai@kernel.org
Cc: bhe@redhat.com
Link: https://lkml.kernel.org/r/1505293975-26005-8-git-send-email-douly.fnst@cn.fujitsu.com