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 <[e-mail]>
Cc: Alexandre Belloni <[e-mail]>
Cc: Claudiu Beznea <[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: Krzysztof Kozlowski <[e-mail]>

drivers/memory/atmel-ebi.c

···
 	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 {