drivers: net: lan865x: Do not read chunks if protected read error detected

The oa_tc6_update_buf_info() function returns error code when read
(protected or not) of OA_BUFSTS has been detected.

In that situation - one shall re-start the interrupt thread handling
(and hence correctly re-read value of this register) than use old
(stalled) RCA(RBA) data to read chunks (which may result in lockup).

Signed-off-by: Lukasz Majewski <lukma@denx.de>