sqm-scripts: Modify installation step to ensure correct file permissions

Use INSTALL_BIN & INSTALL_DATA macros instead of cp
to ensure correct file permissions for the executable files.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
Merge pull request #519 from hnyman/modify-sqm

sqm-scripts: Modify installation step to ensure correct file permissions