Fix SDSUPPORT for MKS SBASE

Fix supplied by @cjsoong in https://github.com/MarlinFirmware/Marlin/issues/8750#issuecomment-350779983

Marlin/src/HAL/HAL_LPC1768/spi_pins.h

@@ -37,6 +37,7 @@
   #define MISO_PIN          P1_23  // J8-3 (moved from EXP2 P0.8)
   #define MOSI_PIN          P2_12  // J8-4 (moved from EXP2 P0.5)
   #define SS_PIN            P0_28
+  #define SD_DETECT_PIN     P0_27
 
 #else
 
@@ -63,9 +64,11 @@
   #ifndef SS_PIN
     #define SS_PIN            P1_23
   #endif
+
+#endif // MKS_SBASE
+
 #ifndef SDSS
   #define SDSS              SS_PIN
 #endif
 
-#endif // MKS_SBASE
-#endif /* SPI_PINS_LPC1768_H */
+#endif // SPI_PINS_LPC1768_H