[arm] Fix gcc.target/arm/g2.c and scd42-2.c for --with-mode=thumb hardfloat targets

[arm] Fix gcc.target/arm/g2.c and scd42-2.c for --with-mode=thumb hardfloat targets

These -mcpu=xscale tests are ARM-only tests and they go to great pains to reject
explicit overriding options, but they're missing the -marm in their dg-options, which means
they will still give that nasty Thumb1 hard-float error when testing an implicit --with-mode=thumb
toolchain (--with-cpu=cortex-a15 --with-fpu=neon-vfpv4 --with-float=hard --with-mode=thumb, for example).

This patch adds the missing -marm and all is good again.

     * gcc.target/arm/g2.c: Add -marm to dg-options.
     * gcc.target/arm/scd42-2.c: Likewise.

From-SVN: r256812