package/busybox: support spaces in module aliases in mdev

The new change which enabled automatic module loading on boot does not handle
the cases when module alias includes spaces. It prevents modules to be loaded
since script fails:

  % find /sys/ -name modalias | xargs sort -u
  sort: /sys/devices/platform/Fixed: No such file or directory

First alias in question is "platform:Fixed MDIO bus".

Amend the script to support above like cases.

Fixes: 07f46c2b ("package/busybox: support automatic module loading with mdev")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>