serial: Fix sh-sci break interrupt/sysrq handling.

The sh-sci sci_br_interrupt() handler was failing to call
in to uart_handle_break(), which was something that only
the SH-3 path was doing, fix that up.

Additionally, SUPPORT_SYSRQ seems to have moved down too
far, move it back to the top so uart_handle_break() and
friends aren't no-ops.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>