[PATCH, libgfortran]: Add "=m" for stmxcsr

[François-Xavier Coudert]

> This patch changes "m" to "=m" for stcxmsr in config/fpu-387.h
>
> 2005-20-13  Uros Bizjak  <uros@kss-loka.si>
>
>         * config/fpu-387.h (set_fpu): Add "=m" for stmxcsr.

OK to commit. (Sorry for the error)

FX