net: stmmac: Refactor FPE functions to generic version

net: stmmac: Refactor FPE functions to generic version

FPE implementation for DWMAC4 and DWXGMAC differs only for:
1) Offset address of MAC_FPE_CTRL_STS and MTL_FPE_CTRL_STS
2) FPRQ(Frame Preemption Residue Queue) field in MAC_RxQ_Ctrl1
3) Bit offset of Frame Preemption Interrupt Enable

Refactor FPE functions to avoid code duplication and
to simplify the code flow by avoiding the use of
function pointers.

Signed-off-by: Furong Xu <0x1207@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/49de4607bae69ffe751b13329a3c07a990b82419.1730449003.git.0x1207@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>