riscv: Cast to float explicitly when comparing a float to an int.

riscv: Cast to float explicitly when comparing a float to an int.

clang 11 complains that the int value is not represented exactly
otherwise which breaks the build. With this case the comparison is
still the same, but since it's explicit the compiler doesn't warn about
it.

Change-Id: I1d9ffc77e778517d9c6a985ae7aa6c4f1d5b57a2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25225
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Alec Roelke <alec.roelke@gmail.com>
Maintainer: Alec Roelke <alec.roelke@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>