arch-arm: Mask out unsupported trapped exception handling bits
arch-arm: Mask out unsupported trapped exception handling bits

Floating-point trapped exception handlings are not currently
supported in gem5, therefore the corresponding bits are RAZ/WI in
FCPR.

Change-Id: Ica43af62d5f3bbc095e8dd872f0bd365231a5b5f
Reviewed-by: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10045
Maintainer: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>

gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,gem5/gem5,gem5/gem5,TUD-OS/gem5-dtu,gem5/gem5,gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,gem5/gem5,gem5/gem5