GCC generates SPE instructions even if -msoft-float is specified.
Explicitly add -mno-spe to prevent generation of SPE instructions.  This
multilib variant must not lead to a usage of the SPE.

gcc/ChangeLog

	* config/rs6000/t-rtems: Add -mno-spe to soft-float multilib for
	MPC8540.

From-SVN: r219385