Pass a void * instead of const char *

Name is not suitable for every platform. Hence, instead of passing const char
*name, it is better to pass a void * which can be used to pass anything to the
serial_open function. For serial_posix, name is required, for serial_ftdi, int
usb_fd is required. Incorporate these as well.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>