pinctrl: uniphier: Annotate struct uniphier_pinctrl_reg_region with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct uniphier_pinctrl_reg_region.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Linus Walleij <[e-mail]>
Cc: Kunihiko Hayashi <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Kees Cook <[e-mail]>
Reviewed-by: "Gustavo A. R. Silva" <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/uniphier/pinctrl-uniphier-core.c

···
 	struct list_head node;
 	unsigned int base;
 	unsigned int nregs;
-	u32 vals[];
+	u32 vals[] __counted_by(nregs);
 };
 
 struct uniphier_pinctrl_priv {