platform/x86: hp-bioscfg: Annotate struct bios_args 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 bios_args.

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

Cc: Jorge Lopez <jorge.lopez2@hp.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Mark Gross <markgross@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tom Rix <trix@redhat.com>
Cc: platform-driver-x86@vger.kernel.org
Cc: llvm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230922175420.work.701-kees@kernel.orgReviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

drivers/platform/x86/hp/hp-bioscfg/biosattr-interface.c

@@ -19,7 +19,7 @@ struct bios_args {
 	u32 command;
 	u32 commandtype;
 	u32 datasize;
-	u8 data[];
+	u8 data[] __counted_by(datasize);
 };
 
 /**