platforms/quickfeather: fix incorrect use of 'is'

Author: sbourdeauducq

migen/build/platforms/quickfeather.py

@@ -54,9 +54,9 @@ def __init__(self, programmer="jlink"):
         self.programmer = programmer
 
     def create_programmer(self):
-        if self.programmer is "jlink":
+        if self.programmer == "jlink":
             return JLinkProgrammer()
-        elif self.programmer is "openocd":
+        elif self.programmer == "openocd":
             return OpenOCD()
         else:
             raise ValueError("{} programmer is not supported"