boards/qemu_x86: fix qemu memory map
boards/qemu_x86: fix qemu memory map

The desired memory map is to have the 0 - 4K page non-present
to catch NULL pointer dereferences,
from 4K - 4MB for the program text (RO, Execute),
ROM (RO, No Execute), and 4MB-8MB for system RAM.

This patch cut text size by 4 KB which allow to meet above
requirements.

Signed-off-by: Andrzej Puzdrowski <0222c24e1773dd88269ed0e559909ec9bea3604a@nordicsemi.no>

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