arm64: defconfig: Enable CONFIG_PINCTRL_MT7622 by default

Recently kernelCI reported the board mt7622-rfb1 has a fail test with
kernel: ERROR: did not start booting whose details could be seen at [1].

The cause is that UART0 can't output anything when it's missing a proper
pin setup with current DTS, so the essential driver is always getting
enabled to fix up the issue.

[1] https://kernelci.org/boot/id/5ad7d62759b51461bfb1f829/



Cc: Kevin Hilman <khilman@baylibre.com>
Cc: stable@vger.kernel.org
Fixes: ae457b76 ("arm64: dts: mt7622: add SoC and peripheral related device nodes")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>