package/hplip: fixup configure.in script for proper autoreconf

This commit adds a minor patch to hplip's configure.in script, which
avoids the need to create the AUTOHRS, ChangeLog, NEWS and README
files before autoreconfiguring, and silences a huge number of warnings
telling to enable the subdir-objects automake option.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>