netconsole: add 'sysdata' suffix to related functions

This commit appends a common "sysdata" suffix to functions responsible
for appending data to sysdata.

This change enhances code clarity and prevents naming conflicts with
other "append" functions, particularly in anticipation of the upcoming
inclusion of the `release` field in the next patch.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250314-netcons_release-v1-3-07979c4b86af@debian.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>