net/szedata2: fix dependency check

net/szedata2: fix dependency check

The library libsze2 provides a pkg-config file: libsze2.pc.
Looking for this .pc file - with dependency() - is preferred
than looking for the library - with cc.find_library().

If the library is not installed in a standard path,
it can be found thanks to PKG_CONFIG_PATH variable.
The previous solution required to use CFLAGS and LDFLAGS
environment variables.

Fixes: 508cfe6be9f1 ("net/szedata2: add to meson build")
Cc: stable@dpdk.org
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Jan Remes <remes@netcope.com>