modules/kmod: Allocate argv with kmalloc_array()

In preparation for converting the kmalloc family of allocators to the
type-aware kmalloc_obj family, we need to make sure that the returned
type from the allocation matches the type of the variable being
assigned. (The kmalloc family returns "void *", which can be implicitly
cast to any pointer type.)

argv holds 5 pointers, but the size was taken from the array type
"char *[5]", which would make the allocation type a pointer to that
array rather than the "char **" being assigned. Allocate 5 entries of
the target's type instead. The resulting allocation size is the same.

Build tested ARCH=x86_64 allmodconfig with GCC 16.2.0:
kernel/module/kmod.o

Assisted-by: LLM coccinelle
Signed-off-by: Kees Cook <kees+treewide@kernel.org>
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>

kernel/module/kmod.c

@@ -81,7 +81,7 @@ static int call_modprobe(char *orig_module_name, int wait)
 	char *module_name;
 	int ret;
 
-	char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
+	char **argv = kmalloc_array(5, sizeof(*argv), GFP_KERNEL);
 	if (!argv)
 		goto out;