tty: n_tty: Add 2 missing parameter descriptions

Fixes the following W=1 kernel build warning(s):

 drivers/tty/n_tty.c:405: warning: Function parameter or member 'tty' not described in 'is_continuation'
 drivers/tty/n_tty.c:1701: warning: Function parameter or member 'flow' not described in 'n_tty_receive_buf_common'

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: "Andrew J. Kroll" <ag784@freenet.buffalo.edu>
Cc: processes-Sapan Bhatia <sapan@corewars.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104193549.4026187-11-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_tty.c

@@ -396,6 +396,7 @@ static inline int is_utf8_continuation(unsigned char c)
 /**
  *	is_continuation		-	multibyte check
  *	@c: byte to check
+ *	@tty: terminal device
  *
  *	Returns true if the utf8 character 'c' is a multibyte continuation
  *	character and the terminal is in unicode mode.
@@ -1668,6 +1669,7 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
  *	@cp: input chars
  *	@fp: flags for each char (if NULL, all chars are TTY_NORMAL)
  *	@count: number of input chars in @cp
+ *	@flow: enable flow control
  *
  *	Called by the terminal driver when a block of characters has
  *	been received. This function must be called from soft contexts