MCP23SXX I/O Expander - SPI (#1068)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

esphome/components/spi/spi.h

@@ -55,6 +55,7 @@ enum SPIDataRate : uint32_t {
   DATA_RATE_2MHZ = 2000000,
   DATA_RATE_4MHZ = 4000000,
   DATA_RATE_8MHZ = 8000000,
+  DATA_RATE_10MHZ = 10000000,
   DATA_RATE_20MHZ = 20000000,
   DATA_RATE_40MHZ = 40000000,
 };