drivers: char: hvc: add arm JTAG DCC console support

This driver adds a basic console that uses the arm JTAG
DCC to transfer data back and forth. It has support for
ARMv6 and ARMv7.

This console is created under the HVC driver, and should be named
/dev/hvcX (or /dev/hvc0 for example).

Cc: Tony Lindgren <tony@atomide.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Daniel Walker <dwalker@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>