translate-all: Change tb_flush() env argument to cpu

translate-all: Change tb_flush() env argument to cpu

All of the core-code usages of this API have the cpu pointer handy so
pass it in. There are only 3 architecture specific usages (2 of which
are commented out) which can just use ENV_GET_CPU() locally to get the
cpu pointer. The reduces core code usage of the CPU env, which brings
us closer to common-obj'ing these core files.

Cc: Riku Voipio <riku.voipio@iki.fi>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>