s390x/tcg: always enable AFP for linux-user

s390x/tcg: always enable AFP for linux-user

linux-user should always enable AFP, otherwise our emulated binary
might crash once it tries to make use of additional floating-point
registers or instructions.

Cc: Peter Maydell <[email protected]>
Cc: Alex Bennée <[email protected]>
Fixes: db0504154e ("s390x/tcg: check for AFP-register, BFP and DFP data exceptions")
Reported-by: Alex Bennée <[email protected]>
Signed-off-by: David Hildenbrand <[email protected]>
Reviewed-by: Thomas Huth <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
Tested-by: Alex Bennée <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Tested-by: Cornelia Huck <[email protected]>
Signed-off-by: Peter Maydell <[email protected]>