ext: Update fputils to rev 0721843

ext: Update fputils to rev 0721843

This patch updates fputils to the latest revision (0721843) from the
upstream repository (github.com/andysan/fputils). This effectively
only updates the license of the library to match gem5's 3-clause BSD
license.

Change-Id: I46d8a5dfac2f4a95e66ee82a15288ac424d7df90
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22125
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>