arm64: defconfig: Add CONFIG_QCOM_RPMPD

RPMPD provides us the CS/MX power domains needed to boot the modem
subsystem on msm8998 for wifi.

Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Link: https://lore.kernel.org/r/20200528184752.4747-1-jeffrey.l.hugo@gmail.com


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>