x86: Call cpu_init_interrupts() from interrupt_init()

Currently cpu_init_interrupts() is called from cpu_init_r() to
setup the interrupt and exception of the cpu core, but at that
time the i8259 has not been initialized to mask all the irqs
and remap the master i8259 interrupt vector base, so the whole
system is at risk of being interrupted, and if interrupted,
wrong interrupt/exception message is shown.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
x86: Remove cpu_init_r() for x86

Since cpu_init_interrupts() was moved out of cpu_init_r(), it is
useless to keep cpu_init_r() for x86, thus remove it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
x86: Refactor interrupt_init()

Rename interrupt_init() in arch/x86/lib/pcat_interrupts.c to
i8259_init() and create a new interrupt_init() in
arch/x86/cpu/interrupt.c to call i8259_init() followed by a
call to cpu_init_interrupts().

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
x86: Remove unnecessary call to initr_enable_interrupts()

Actually initr_enable_interrupts() was never called in an x86 build
due to it was wrapped by CONFIG_x86 (typo of X86).

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>