util/kconfig: Uprev to Linux 6.2's kconfig

The upstream build system uses a newly introduced function `read-file`,
so copy that in from Linux 6.2.

TEST=`util/abuild/abuild -C` output (config.h and config.build) remains
the same

Change-Id: Ic100bf189ebd3eaa0eb26904ae8602910329a180
Signed-off-by: Patrick Georgi <patrick@coreboot.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79179
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>

util/kconfig/mconf.c

@@ -163,6 +163,12 @@ static const char mconf_readme[] =
 "(especially with a larger number of unrolled categories) than the\n"
 "default mode.\n"
 "\n"
+
+"Search\n"
+"-------\n"
+"Pressing the forward-slash (/) anywhere brings up a search dialog box.\n"
+"\n"
+
 "Different color themes available\n"
 "--------------------------------\n"
 "It is possible to select different color themes using the variable\n"
@@ -442,9 +448,8 @@ again:
 
 		res = get_relations_str(sym_arr, &head);
 		set_subtitle();
-		dres = show_textbox_ext("Search Results", (char *)
-					str_get(&res), 0, 0, keys, &vscroll,
-					&hscroll, &update_text, (void *)
+		dres = show_textbox_ext("Search Results", str_get(&res), 0, 0,
+					keys, &vscroll, &hscroll, &update_text,
 					&data);
 		again = false;
 		for (i = 0; i < JUMP_NB && keys[i]; i++)