x86/apic: Fix spelling mistake: "symmectic" -> "symmetric"

Trivial fix to spelling mistakes in pr_info messages

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dou Liyang <douly.fnst@cn.fujitsu.com>
Link: https://lkml.kernel.org/r/20170927102223.31920-1-colin.king@canonical.com