fix for trinket/gemma m0

Author: ladyada

libraries/SPI/SPI.cpp

@@ -405,8 +405,12 @@ static const struct {
   { &SERCOM1->SPI.DATA.reg, SERCOM1_DMAC_ID_TX, SERCOM1_DMAC_ID_RX },
   { &SERCOM2->SPI.DATA.reg, SERCOM2_DMAC_ID_TX, SERCOM2_DMAC_ID_RX },
   { &SERCOM3->SPI.DATA.reg, SERCOM3_DMAC_ID_TX, SERCOM3_DMAC_ID_RX },
+#if defined(SERCOM4)
   { &SERCOM4->SPI.DATA.reg, SERCOM4_DMAC_ID_TX, SERCOM4_DMAC_ID_RX },
+#endif
+#if defined(SERCOM5)
   { &SERCOM5->SPI.DATA.reg, SERCOM5_DMAC_ID_TX, SERCOM5_DMAC_ID_RX },
+#endif
 #if defined(SERCOM6)
   { &SERCOM6->SPI.DATA.reg, SERCOM6_DMAC_ID_TX, SERCOM6_DMAC_ID_RX },
 #endif