net: stmmac: refactor clock management in EQoS driver

Refactor clock management in EQoS driver for code reuse and to avoid
redundancy. This way, only minimal changes are required when a new platform
is added.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Swathi K S <swathi.ks@samsung.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250213041559.106111-1-swathi.ks@samsung.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>