stmmac: Revert "stmmac: align RX buffers"

This reverts commit a955318f ("stmmac: align RX buffers"),
which breaks at least one platform (Nvidia Jetson-X1), causing
packet corruption. This is 100% reproducible, and reverting
the patch results in a working system again.

Given that it is "only" a performance optimisation, let's
return to a known working configuration until we can have a
good understanding of what is happening here.

Fixes: a955318f

 ("stmmac: align RX buffers")
Cc: Matteo Croce <mcroce@linux.microsoft.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Link: https://lore.kernel.org/netdev/871r71azjw.wl-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210820183002.457226-1-maz@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>