target-i386: fix set of registers zeroed on reset

target-i386: fix set of registers zeroed on reset

BND0-3, BNDCFGU, BNDCFGS, BNDSTATUS were not zeroed on reset, but they
should be (Intel Instruction Set Extensions Programming Reference
319433-015, pages 9-4 and 9-6).  Same for YMM.

XCR0 should be reset to 1.

TSC and TSC_RESET were zeroed already by the memset, remove the explicit
assignments.

Cc: Andreas Faerber <afaerber@suse.de>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>