iio: health: max30100: fixed parenthesis around FIFO count check

FIFO was being read every sample after the "almost full" state was
reached. This was due to an incorrect placement of the parenthesis
in the while condition check.

Note - the fixes tag is not actually correct, but the fix in this patch
would also be needed for it to function correctly so we'll go with that
one.  Backports should pick up both.

Signed-off-by: Matt Ranostay <matt@ranostay.consulting>
Fixes: b74fccad ("iio: health: max30100: correct FIFO check condition")
Cc: Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>