buildtools: zero elf info variable in pmdinfogen

buildtools: zero elf info variable in pmdinfogen

This commit zeros out the elf_info struct at startup of the
pmdinfogen code. If it is not zeroed, later in the code gcc
produces "may be unused" prints. Clang does not report any
issue.

This issue is only observed when compiling pmdinfogen as an
optimized build, hence this warning is not disabled in the
existing Makefile.

This commit enables a simplification in the meson build
system, removing the requirement for "-Wno-maybe-uninitialized".

Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>