parisc: kernel: using strlcpy() instead of strcpy()

'boot_args' is an input args, and 'boot_command_line' has a fix length.
So use strlcpy() instead of strcpy() to avoid memory overflow.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Acked-by: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Helge Deller <deller@gmx.de>