arch/x86: inline x2APIC EOI

From the Jailhouse days, this has been a function call. That's silly.
We now inline the EOI in the ISR when in x2APIC mode. Also clean up
z_irq_controller_eoi(), so it now uses the inline macros.

Also, we now enable x2APIC on up_squared by default.

Fixes: #17133

Signed-off-by: Charles E. Youse <charles.youse@intel.com>