[arm] Fix gcc.target/arm/pr40887.c directives

[arm] Fix gcc.target/arm/pr40887.c directives

This patch converts gcc.target/arm/pr40887.c to use the proper effective target check and dg-add-options for armv5te
so that we avoid situations where we end up trying to compile the test with a Thumb1 hard-float ABI, which makes the
compiler complain.

This allows the test to pass gracefully for me for my compiler configured with:
--with-cpu=cortex-a15 --with-fpu=neon-vfpv4 --with-float=hard --with-mode=thumb

     * gcc.target/arm/pr40887.c: Add armv5te effective target checks and
     directives.

From-SVN: r256784