kconfig: Removed prompt for TEXT_SECTION_OFFSET when MCUboot is used
kconfig: Removed prompt for TEXT_SECTION_OFFSET when MCUboot is used

When this syntax is used for the type definition:

hex "TEXT section offset"

Kconfig expect the user to enter the value for TEXT_SECTION_OFFSET and
the defaut value for BOOTLOADER_MCUBOOT is not used. Changing the syntax
to this:

hex
	prompt "TEXT section offset" if !BOOTLOADER_MCUBOOT

will tell Kconfig that TEXT_SECTION_OFFSET will not be set by the user
when BOOTLOADER_MCUBOOT is set and then Kconfig will use the default
value.

Signed-off-by: Ole Sæther <0776186c6ce37cfe0a4dc852b0a8d49dd73a9f0f@nordicsemi.no>

galak/zephyr,finikorg/zephyr,explora26/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,Vudentz/zephyr,ldts/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,ldts/zephyr,nashif/zephyr,explora26/zephyr,explora26/zephyr,ldts/zephyr,Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,ldts/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,ldts/zephyr,Vudentz/zephyr