net: stmmac: Relocate extern declarations in common.h and hwif.h

net: stmmac: Relocate extern declarations in common.h and hwif.h

The extern declarations should be in a header file that corresponds to
their definition, move these extern declarations to its header file.
Some of them have nowhere to go, so move them to hwif.h since they are
referenced in hwif.c only.

dwmac100_* dwmac1000_* dwmac4_* dwmac410_* dwmac510_* stay in hwif.h,
otherwise you will be flooded with name conflicts from dwmac100.h,
dwmac1000.h and dwmac4.h if hwif.c try to #include these .h files.

Compile tested only.
No functional change intended.

Suggested-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Furong Xu <0x1207@gmail.com>
Link: https://patch.msgid.link/20241208070202.203931-1-0x1207@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>