memory: atmel-ebi: Annotate struct atmel_ebi_dev 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 atmel_ebi_dev.

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

Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230922175215.work.122-kees@kernel.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

drivers/memory/atmel-ebi.c

@@ -30,7 +30,7 @@ struct atmel_ebi_dev {
 	struct atmel_ebi *ebi;
 	u32 mode;
 	int numcs;
-	struct atmel_ebi_dev_config configs[];
+	struct atmel_ebi_dev_config configs[] __counted_by(numcs);
 };
 
 struct atmel_ebi_caps {