net: phy: update outdated comment for removed phy_package_read/write()

net: phy: update outdated comment for removed phy_package_read/write()

The locked convenience functions phy_package_read() and
phy_package_write() were removed (as they had no users) by commit
e7f984e925d2 ("net: phy: move PHY package related code from phy.h
to phy_package.c").  Update the comment to reference the existing
unlocked counterparts __phy_package_read() and __phy_package_write().

Assisted-by: unnamed:deepseek-v3.2 coccinelle
Signed-off-by: Kexin Sun <kexinsun@smail.nju.edu.cn>
Link: https://patch.msgid.link/20260321105825.7221-1-kexinsun@smail.nju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>