regulator: mc13xxx: Annotate struct mc13xxx_regulator_priv 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 mc13xxx_regulator_priv.

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

Cc: Liam Girdwood <[e-mail]>
Cc: Mark Brown <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/mc13xxx.h

···
 	u32 powermisc_pwgt_state;
 	struct mc13xxx_regulator *mc13xxx_regulators;
 	int num_regulators;
-	struct regulator_dev *regulators[];
+	struct regulator_dev *regulators[] __counted_by(num_regulators);
 };
 
 extern int mc13xxx_fixed_regulator_set_voltage(struct regulator_dev *rdev,