libkmod: Handle long lines in /proc/modules

libkmod: Handle long lines in /proc/modules

kmod_module_new_from_loaded() calls fgets with a 4k buffer. When a
module such as usbcore is used by too many modules, the rest of the line
is considered a beginning of another lines and we eventually get errors
like these from lsmod:

libkmod: kmod_module_get_holders: could not open '/sys/module/100,/holders': No such file or directory

together with bogus entries in the output. In kmod_module_get_size, the
problem does not affect functionality, but the line numbers in error
messages will be wrong.

Signed-off-by: Michal Marek <mmarek@suse.com>