Nuttx: fixups after rebase on Linux

Seems that mavlink_receiver_linux.cpp inherited the history
from mavlink_receiver.cpp so updates went to it vs mavlink_receiver_nuttx.cpp

Two module.mk files used ifdef instead of ifeq.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/drivers/drv_led.h

@@ -39,6 +39,7 @@
 
 #pragma once
 
+#include <px4_defines.h>
 #include <stdint.h>
 #include <sys/ioctl.h>
 

src/drivers/hil/module.mk

@@ -37,7 +37,7 @@
 
 MODULE_COMMAND	= hil
 
-ifdef ($(PX4_TARGET_OS),nuttx)
+ifeq ($(PX4_TARGET_OS),nuttx)
 SRCS		= hil.cpp
 MAXOPTIMIZATION	 = -Os
 else