[Silabs][SiWx917]Re-add enable_wifi_ipv4 arg in ligthing-app

[jmartinez-silabs]

PR #25591 moved the chip_enable_wifi_ipv4 build argument to a common location for EFR32 platform.
This change was not extended to the siwx917 platform except for a removal in 1 build.gn.

Siwx917 requires a build file clean up/refactor.
For now, just re-add the argument to the siwx917 lighting-app like it was before so the app can build in the mean time.

[github-actions]

PR #25670: Size comparison from b02a6ca to d1fd10f

Decreases (1 build for cc32xx)

platform	target	config	section	b02a6ca	d1fd10f	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20245970	20245969	-1	-0.0

Full report (4 builds for cc32xx, mbed, qpg)

platform	target	config	section	b02a6ca	d1fd10f	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	645489	645489	0	0.0
			(read/write)	203848	203848	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197248	197248	0	0.0
			.comment	194	194	0	0.0
			.data	1480	1480	0	0.0
			.debug_abbrev	930293	930293	0	0.0
			.debug_aranges	87384	87384	0	0.0
			.debug_frame	300248	300248	0	0.0
			.debug_info	20245970	20245969	-1	-0.0
			.debug_line	2660979	2660979	0	0.0
			.debug_loc	2804893	2804893	0	0.0
			.debug_ranges	283168	283168	0	0.0
			.debug_str	3026947	3026947	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	106009	106009	0	0.0
			.shstrtab	232	232	0	0.0
			.stab	204	204	0	0.0
			.stabstr	441	441	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	380271	380271	0	0.0
			.symtab	257312	257312	0	0.0
			.text	537360	537360	0	0.0
mbed	lock-app	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	2468312	2468312	0	0.0
			.bss	215964	215964	0	0.0
			.data	5880	5880	0	0.0
			.text	1430956	1430956	0	0.0
qpg	lighting-app	qpg6105+debug	(read/write)	1153444	1153444	0	0.0
			.bss	100076	100076	0	0.0
			.data	852	852	0	0.0
			.text	600540	600540	0	0.0
	lock-app	qpg6105+debug	(read/write)	1120300	1120300	0	0.0
			.bss	96468	96468	0	0.0
			.data	864	864	0	0.0
			.text	567400	567400	0	0.0