iio: magnetometer: fix if () scoped_guard() formatting

Add mising braces after an if condition that contains scoped_guard().

This style is both preferred and necessary here, to fix warning after
scoped_guard() change in commit fcc22ac5 ("cleanup: Adjust
scoped_guard() macros to avoid potential warning") to have if-else inside
of the macro. Current (no braces) use in af8133j_set_scale() yields
the following warnings:
af8133j.c:315:12: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
af8133j.c:316:3: warning: add explicit braces to avoid dangling else [-Wdangling-else]

Fixes: fcc22ac5 ("cleanup: Adjust scoped_guard() macros to avoid potential warning")
Closes: https://lore.kernel.org/oe-kbuild-all/202409270848.tTpyEAR7-lkp@intel.com/


Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20241108154258.21411-1-przemyslaw.kitszel@intel.com