LF-1723: spi: lpspi: run transfer speed_hz sanity check

commit 779ed133e9da4c649d9586f6a88049cf884c081a from
git://source.codeaurora.org/external/qoriq/qoriq-components/linux

Coverity reports Division or modulo by zero potential issue(CWE-369)
about the provided transfer speed_hz. Run sanity check first to avoid this
problem.

Signed-off-by: Han Xu <han.xu@nxp.com>
Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
Reviewed-by: Jun Li <jun.li@nxp.com>
Acked-by: Jason Liu <jason.hui.liu@nxp.com>
Signed-off-by: Meng Li <Meng.Li@windriver.com>