drivers/tty: don't use the byte channel handle as a parameter in ehv_bytechan.c

The ePAPR hypervisor byte channel console driver only supports one byte
channel as a console, and the byte channel handle is stored in a global
variable.  It doesn't make any sense to pass that handle as a parameter
to the console functions, since these functions already have access to the
global variable.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>