package/pkg-utils.mk: introduce "name" field in show-info output

The keys of the JSON dict returned by "make show-info" is the package
name, including the "host-" prefix for host packages.

However, it is sometimes useful to get the actual name of the package,
without the "host-" prefix, so we add a "name" property that holds the
"raw name" of the package.

Suggested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>