soc: qcom: smd: Remove standalone driver

Remove the standalone SMD implementation as we have transitioned the
client drivers to use the RPMSG based one.

Also remove all dependencies on QCOM_SMD from Kconfig files, in order to
keep them selectable in the absence of the removed symbol.

Acked-by: Andy Gross <andy.gross@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>