net: stmmac: Add generic suspend/resume helper for PCI-based controllers

net: stmmac: Add generic suspend/resume helper for PCI-based controllers

Most glue driver for PCI-based DWMAC controllers utilize similar
platform suspend/resume routines. Add a generic implementation to reduce
duplicated code.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Yanteng Si <siyanteng@cqsoftware.com.cn>
Link: https://patch.msgid.link/20251124160417.51514-2-ziyao@disroot.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>