spi: cadence: Add ARM dependency

In Kconfig, add ARM dependency because readl/writel_relaxed are used.
Remove dependency on SPI_MASTER as this is already under "if SPI_MASTER".

Signed-off-by: Harini Katakam <harinik@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>