Remove XFAILs from fmaxmin test

These appears to have been resolved by compiling the test with -fno-builtin
and/or using a newer compiler.

PR: 208703
Reviewed By: ngie
Differential Revision: https://reviews.freebsd.org/D28884

(cherry picked from commit b358534ab1a953fac5830012751232e2f0807cc0)