net: phy: realtek: remove unsed RTL821x_PHYSR* macros

These macros have there since the first revision but were never used, so
let's just remove them.

Signed-off-by: Michael Klein <michael@fossekall.de>
Link: https://patch.msgid.link/20250504172916.243185-2-michael@fossekall.de


Signed-off-by: Paolo Abeni <pabeni@redhat.com>