target/arm: Set VFP-related MVFR0 fields for arm926 and arm1026

target/arm: Set VFP-related MVFR0 fields for arm926 and arm1026

The ARMv5 architecture didn't specify detailed per-feature ID
registers. Now that we're using the MVFR0 register fields to
gate the existence of VFP instructions, we need to set up
the correct values in the cpu->isar structure so that we still
provide an FPU to the guest.

This fixes a regression in the arm926 and arm1026 CPUs, which
are the only ones that both have VFP and are ARMv5 or earlier.
This regression was introduced by the VFP refactoring, and more
specifically by commits 1120827fa182f0e76 and 266bd25c485597c,
which accidentally disabled VFP short-vector support and
double-precision support on these CPUs.

Fixes: 1120827fa182f0e
Fixes: 266bd25c485597c
Fixes: https://bugs.launchpad.net/qemu/+bug/1836192
Reported-by: Christophe Lyon <christophe.lyon@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Christophe Lyon <christophe.lyon@linaro.org>
Message-id: 20190711131241.22231-1-peter.maydell@linaro.org