net: enetc: use EXPORT_SYMBOL_GPL for enetc_phc_index

stable inclusion
from stable-v5.10.195
commit 1aeb76ffdfc04eae59d702acb125a7c76a464fcd
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I95JOC

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1aeb76ffdfc04eae59d702acb125a7c76a464fcd



--------------------------------

commit 569820be upstream.

enetc_phc_index is only used via symbol_get, which was only ever
intended for very internal symbols like this one.  Use EXPORT_SYMBOL_GPL
for it so that symbol_get can enforce only being used on
EXPORT_SYMBOL_GPL symbols.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>