Fix script to build mac80211_hwsim kernel module

[abeltrano]

Type

• Bug fix
• Feature addition
• Feature update
• Documentation
• Build Infrastructure

Side Effects

• Breaking change
• Non-functional change

Goals

• Ensure the mac80211_hwsim module can be built on newer kernels (5.15.133.1+).

Technical Details

• Enable CONFIG_WLAN feature in case the default ever changes to be disabled, or, if the running kernel has it disabled.
• Move kernel and module prep to after kernel configuration is set.

Test Results

• Rebuilt kernel with script from scratch and verified mac80211_hwsim was build and could be loaded with modprobe.

Reviewer Focus

• Consider whether there is any configuration where this sequence of build steps would not work.

Future Work

• Hopefully, none.

Checklist

• Build target all compiles cleanly.
• clang-format and clang-tidy deltas produced no new output.
• Newly added functions include doxygen-style comment block.