greybus: gpbridge.h: remove BIT() define

It's up to other files to define this if it's not present, not this
file.
Reported-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/gpbridge.h

@@ -268,9 +268,6 @@ struct gb_pwm_disable_request {
 };
 
 /* I2S */
-#ifndef BIT
-#define BIT(n) (1UL << (n))
-#endif
 
 #define GB_I2S_MGMT_TYPE_PROTOCOL_VERSION		0x01
 #define GB_I2S_MGMT_TYPE_GET_SUPPORTED_CONFIGURATIONS	0x02