[PATCH] math: Fix ilogb(double) return type

Signed-off-by: Aaron Watry <awatry@gmail.com>

Signed-off-by: Aaron Watry <awatry@gmail.com>
CC: Jan Vesely <jan.vesely@rutgers.edu>

LGTM. sorry I did not catch it during review.
Reviewed-by: Jan Vesely <jan.vesely@rutgers.edu>