pa_stats is optional in dt bindings, make it optional in driver as well.
Currently if pa_stats syscon regmap is not found driver returns -ENODEV.
Fix this by not returning an error in case pa_stats is not found and
continue generating ethtool stats without pa_stats.

Fixes: 550ee90a ("net: ti: icssg-prueth: Add support for PA Stats")
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20240906093649.870883-1-danishanwar@ti.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>