Add line request bias flags

The GPIOD_LINE_REQUEST_FLAG_BIAS_* flags were added in libgpiod 1.5

Author: uSpike

asyncgpio/libgpiod.py

@@ -76,6 +76,9 @@
     GPIOD_LINE_REQUEST_FLAG_OPEN_DRAIN = 1,
     GPIOD_LINE_REQUEST_FLAG_OPEN_SOURCE = 2,
     GPIOD_LINE_REQUEST_FLAG_ACTIVE_LOW = 4,
+    GPIOD_LINE_REQUEST_FLAG_BIAS_DISABLE = 8,
+    GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_DOWN = 16,
+    GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_UP = 32,
 };
 
 enum {