eglibc: Add missing ${PN} and ${PKGSUFFIX} usages

eglibc: Add missing ${PN} and ${PKGSUFFIX} usages

This fixes warning messages such as:

The providers found were: ['virtual:nativesdk:eglibc_2.13.bb', 'eglibc_2.13.bb']
The PREFERRED_PROVIDER entries resulting in this conflict were: ['PREFERRED_PROVIDER_virtual/libc-nativesdk = eglibc-nativesdk', 'PREFERRED_PROVIDER_virtual/libc = eglibc']
NOTE: multiple providers are available for runtime glibc-utils (eglibc, eglibc-nativesdk, external-csl-toolchain, external-poky-toolchain)
NOTE: consider defining a PREFERRED_PROVIDER entry to match glibc-utils

This highlights how ugly adding to PN is when using BBCLASSEXTEND. We need to do this to
eglibc so the nativesdk class continues to work correctly for now and ensure consistency
in how the various eglibc packages are generated.

Longer term, if we switch nativesdk to use the multilib approach and MLPREFIX, we can
remove all the PKGSUFFIX mess. I'd rather not get into changing nativesdk right at this
time though given all the other changes that are going on.

(From OE-Core rev: 3a18aa65a4c123ea922b6cd09ca6a77090f12252)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>