gpsd: disable xmlto

* xmlto is used if xsltproc test fails
  xstlproc is found in sysroot right, but then it's tested like this:
  sysroots/x86_64-linux/usr/bin/xsltproc --nonet --noout http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl conftest.xml
  and that fails if there isn't right docbook.xsl on host
  /usr/share/sgml/docbook/xsl-stylesheets/manpages/docbook.xsl
* xmlto then fails with:
  xmlto  man './gps.xml'
  | xmlto: /var/lib/jenkins/jobs/shr-core-branches/workspace/shr-core/tmp-eglibc/work/armv7a-vfp-neon-oe-linux-gnueabi/gpsd-2.96-r1/gpsd-2.96/./gps.xml does not validate (status 3)
  | xmlto: Fix document syntax or use --skip-validation option
  | I/O error : Attempt to load network entity http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd
  | /var/lib/jenkins/jobs/shr-core-branches/workspace/shr-core/tmp-eglibc/work/armv7a-vfp-neon-oe-linux-gnueabi/gpsd-2.96-r1/gpsd-2.96/./gps.xml:8: warning: failed to load external entity "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"
  |    "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
  |                                                               ^
  | /var/lib/jenkins/jobs/shr-core-branches/workspace/shr-core/tmp-eglibc/work/armv7a-vfp-neon-oe-linux-gnueabi/gpsd-2.96-r1/gpsd-2.96/./gps.xml:133: parser error : Entity 'mdash' not defined
  | should default to using for display — imperial, nautical, or
  |                                            ^
  | I/O error : Attempt to load network entity http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd
  | warning: failed to load external entity "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"
  | validity error : Could not load the external subset "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd

"
  | Document /var/lib/jenkins/jobs/shr-core-branches/workspace/shr-core/tmp-eglibc/work/armv7a-vfp-neon-oe-linux-gnueabi/gpsd-2.96-r1/gpsd-2.96/./gps.xml does not validate
* without xstlproc and xmlto it disables man pages building
  configure:18182: WARNING: Neither xsltproc nor xmlto works: I will not build man pages.
  configure:18184: WARNING: To build man pages, install xsltproc/xsltlib or xmlto and run autogen.sh again.
* this can be reverted as soon as there is working xmlto using OE
  provided DTDs in DEPENDS

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>