ethos-u-vela: Fix runtime dependencies

[tq-steina]

vela imports pkg_resources module, so this needs to added to RDEPENDS.

See https://github.com/nxp-imx/ethos-u-vela/blob/lf-6.1.1_1.0.0/ethosu/vela/_version.py#L16 for the actual import.
Fixes the error backtrace:

root@tqma93xxla-mba93xxla:/usr/lib/python3.10# vela
Traceback (most recent call last):
  File "/usr/bin/vela", line 5, in <module>
    from ethosu.vela.vela import main
  File "/usr/lib/python3.10/site-packages/ethosu/vela/__init__.py", line 16, in <module>
    from ._version import __version__
  File "/usr/lib/python3.10/site-packages/ethosu/vela/_version.py", line 16, in <module>
    import pkg_resources
ModuleNotFoundError: No module named 'pkg_resources'