Input: do not overwrite the first part of phys string

Use strlcat() to append a string to the previously created first part.

Signed-off-by: Márton Németh <nm127@freemail.hu>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>