tcg/arm: Clarify tcg_out_bx for arm4 host

In theory this would re-enable usage of QEMU on an armv4 host.
Whether this is worthwhile is debatable -- we've been unconditionally
issuing the armv5t BX instruction in the prologue since 2011 without
complaint.  Possibly we should simply require an armv6 host.

Signed-off-by: Richard Henderson <rth@twiddle.net>
1 file changed