struct fs_platform_info is only used in fs_enet ethernet driver since
commit 3dd82a1e ("[POWERPC] CPM: Always use new binding.").

Stale prototypes using fs_platform_info were left over in
arch/powerpc/sysdev/fsl_soc.c but they are now removed by
previous patch.

Move struct fs_platform_info into fs_enet.h
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/f882d6b0b7075d0d8435310634ceaa2cc8e9938f.1691155347.git.christophe.leroy@csgroup.euSigned-off-by: Jakub Kicinski <kuba@kernel.org>