Merge pull request #15 from lurch/patch-1

Fix import in pio_spi.py

pio/pio_spi.py

@@ -1,4 +1,4 @@
-from rp2 import PIO, asm_pio
+import rp2
 from machine import Pin
 
 @rp2.asm_pio(out_shiftdir=0, autopull=True, pull_thresh=8, autopush=True, push_thresh=8, sideset_init=(rp2.PIO.OUT_LOW, rp2.PIO.OUT_HIGH), out_init=rp2.PIO.OUT_LOW)