Kconfig: build system ignores configs for snps/nsim SoCs after HWMv2 was applied

[kokas-a]

Describe the bug
After HWMv2 model was applied, build system ignores config XIP that configured on SoC level of Kconfig.

Synopsys nSIM platforms has following levels of XIP configs:

1. arch/Kconfig applied for ARC architecture in general via imply XIP
2. soc/snps/nsim/Kconfig.defconfig via default n
3. (optional) board/snps/nsim/ ${board}_defconfig

If XIP configuration is not set on board level explicitly, then 2nd level (SoC-level) config is also skipped. And final configuration is taken from arch-level via imply XIP and assigned with XIP=y value.

To Reproduce
Steps to reproduce the behavior:

1. west build -b nsim/nsim_em samples/hello_world
2. cat build/zephyr/.config | grep XIP
3. See incorrect behavior: CONFIG_XIP=y

Expected behavior
CONFIG_XIP=n in .config file, as config XIP was not explicitly defined on board level. It defined with n value on SoC level.

Environment (please complete the following information):

• OS: LInux
• Toolchain: Zephyr SDK, ARCMWDT
• Commit SHA ff58bd0 or just main

[kokas-a]

The issue touches not only ARC nSIM platforms. For example, tlsr9518adk80d board has the same way of including XIP configs, and final result is CONFIG_XIP=y despite it turned off on SoC level.