iio: proximity: sx9324: add empty line in front of bullet list

"make htmldocs" emits a warning of:

Documentation/ABI/testing/sysfs-bus-iio-sx9324:2: WARNING: Unexpected indentation.

This is due to a missing empty line in front of the bullet list.
Fix it.

Note: The line count of 2 in the warning is not exact in this case.

Signed-off-by: Akira Yokosawa <[e-mail]>
Fixes: 4c18a890dff8 ("iio:proximity:sx9324: Add SX9324 support")
Link: https://lore.kernel.org/r/[e-mail]/
Reported-by: kernel test robot <[e-mail]>
Cc: Gwendal Grignou <[e-mail]>
Cc: Stephen Boyd <[e-mail]>
Cc: Jonathan Cameron <[e-mail]>
Reviewed-by: Bagas Sanjaya <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/ABI/testing/sysfs-bus-iio-sx9324

···
 Description:
 		SX9324 has 3 inputs, CS0, CS1 and CS2. Hardware layout
 		defines if the input is
+
 		+ not connected (HZ),
 		+ grounded (GD),
 		+ connected to an antenna where it can act as a base