hdparm: prevent package makefile from stripping the hdparm binary

Packages shouldn't strip executables by themselves, so that Buildroot
controls whether stripping should occur or not. This also fixes the
build on Blackfin FLAT where stripping actually doesn't work because
stripping FLAT binaries is not supported.

Fixes:

  http://autobuild.buildroot.org/results/7d4/7d4e59c96928a06db5091235bf2eacf462ba8a21/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>