Read 32 bits RX info to a local variable to fix race condition between
reading RX length and RX tag.

Another solution is to get RX tag at first statement, but adopted solution
can save some memory read, and also save 15 bytes binary code.

RX tag, a sequence number, is used to ensure that RX data has been DMA to
memory completely, so driver must check sequence number is expected before
reading other data.

This potential problem happens only after enabling 36-bit DMA.
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://msgid.link/20240611021901.26394-2-pkshih@realtek.com