iio: stmpe-adc: Use correctly sized arguments for bit field

The find.h APIs are designed to be used only on unsigned long arguments.
This can technically result in a over-read, but it is harmless in this
case. Regardless, fix it to avoid the warning seen under -Warray-bounds,
which we'd like to enable globally:

In file included from ./include/linux/bitmap.h:9,
                 from ./include/linux/cpumask.h:12,
                 from ./arch/x86/include/asm/cpumask.h:5,
                 from ./arch/x86/include/asm/msr.h:11,
                 from ./arch/x86/include/asm/processor.h:22,
                 from ./arch/x86/include/asm/cpufeature.h:5,
                 from ./arch/x86/include/asm/thread_info.h:53,
                 from ./include/linux/thread_info.h:60,
                 from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:55,
                 from ./include/linux/swait.h:7,
                 from ./include/linux/completion.h:12,
                 from drivers/iio/adc/stmpe-adc.c:10:
drivers/iio/adc/stmpe-adc.c: In function 'stmpe_adc_probe':
./include/linux/find.h:98:23: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Warray-bounds]
   98 |                 val = *addr | ~GENMASK(size - 1, offset);
      |                       ^~~~~
drivers/iio/adc/stmpe-adc.c:258:13: note: while referencing 'norequest_mask'
  258 |         u32 norequest_mask = 0;
      |             ^~~~~~~~~~~~~~

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/stmpe-adc.c

@@ -256,6 +256,7 @@ static int stmpe_adc_probe(struct platform_device *pdev)
 	struct stmpe_adc *info;
 	struct device_node *np;
 	u32 norequest_mask = 0;
+	unsigned long bits;
 	int irq_temp, irq_adc;
 	int num_chan = 0;
 	int i = 0;
@@ -309,8 +310,8 @@ static int stmpe_adc_probe(struct platform_device *pdev)
 
 	of_property_read_u32(np, "st,norequest-mask", &norequest_mask);
 
-	for_each_clear_bit(i, (unsigned long *) &norequest_mask,
-			   (STMPE_ADC_LAST_NR + 1)) {
+	bits = norequest_mask;
+	for_each_clear_bit(i, &bits, (STMPE_ADC_LAST_NR + 1)) {
 		stmpe_adc_voltage_chan(&info->stmpe_adc_iio_channels[num_chan], i);
 		num_chan++;
 	}