arch: x86: core: pcie: rephrase use of ain't
arch: x86: core: pcie: rephrase use of ain't

Rephrasing away from ain't, which is informal, uncommon, and can
be viewed as substandard or 'slang'.

Signed-off-by: Jennifer Williams <7953176682adde4345743ea99dbf2682fb898b9d@intel.com>

zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,galak/zephyr