mfd: iqs62x: Annotate struct iqs62x_fw_blk 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 iqs62x_fw_blk.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocciSigned-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230922175337.work.150-kees@kernel.orgSigned-off-by: Lee Jones <lee@kernel.org>

drivers/mfd/iqs62x.c

@@ -96,7 +96,7 @@ struct iqs62x_fw_blk {
 	u8 addr;
 	u8 mask;
 	u8 len;
-	u8 data[];
+	u8 data[] __counted_by(len);
 };
 
 struct iqs62x_info {