hp5590: Fix compile error
Fixes build error due to wrong #include path. The configure step has been done as follows (the options are the same as what Ubuntu ships with):
PREFIX="$(pwd)/../build-install"
env CFLAGS="-g -Og" ../configure \
--prefix=$PREFIX \
--libdir=$PREFIX/lib \
--sysconfdir=/etc \
--localstatedir=/var \
--datadir=$PREFIX/share \
--mandir=$PREFIX/share/man \
--with-docdir=$PREFIX/share/doc/libsane \
--disable-locking \
--enable-static \
--enable-pthread \
--with-gphoto2 \
--enable-translations \
--enable-avahi \
--enable-pnm-backend \
--with-usb \
--without-api-spec \
--without-v4l
Version of sane-backends: Git: 1a2a8ee7