arm: dcc_tty: fix armv6 dcc tty build failure

arm: dcc_tty: fix armv6 dcc tty build failure

Fix spinlock declaration and tty_insert/flip arguments.

If ARM DCC tty driver is enabled then we run into following build failure:
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  CC      drivers/char/dcc_tty.o
drivers/char/dcc_tty.c:29:36: error: ‘SPIN_LOCK_UNLOCKED’ undeclared here (not in a function)
drivers/char/dcc_tty.c: In function ‘dcc_poll_locked’:
drivers/char/dcc_tty.c:83:4: warning: passing argument 1 of ‘tty_insert_flip_string’ from incompatible pointer type [enabled by default]
In file included from drivers/char/dcc_tty.c:23:0:
include/linux/tty_flip.h:32:19: note: expected ‘struct tty_port *’ but argument is of type ‘struct tty_struct *’
drivers/char/dcc_tty.c:84:4: warning: passing argument 1 of ‘tty_flip_buffer_push’ from incompatible pointer type [enabled by default]
In file included from drivers/char/dcc_tty.c:23:0:
include/linux/tty_flip.h:13:13: note: expected ‘struct tty_port *’ but argument is of type ‘struct tty_struct *’
make[2]: *** [drivers/char/dcc_tty.o] Error 1
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Signed-off-by: Amit Pundir <amit.pundir@linaro.org>