remove machine_i2c, machine_spi

This micropython code is not used in circuitpython

Author: jepler

extmod/machine_spi.c

@@ -161,8 +161,6 @@ PY_EXTMOD_O_BASENAME += \
 	extmod/machine_pinbase.o \
 	extmod/machine_signal.o \
 	extmod/machine_pulse.o \
-	extmod/machine_i2c.o \
-	extmod/machine_spi.o
 
 LIB_SRC_C = $(addprefix lib/,\
 	$(LIB_SRC_C_EXTRA) \