1.Add sbus driver for linux . This driver can be used to read the

inverted S.bus signal and fetch the data of each channel and publish it

2. Fix the bug of linux_pwm_out, when the protocol is pca9685,
after the init method is executed,the method of determining the return
value of init method is incorrect,this will cause the driver to fail

3. Add linux_sbus driver to other posix prefixes cmake files

cmake/configs/posix_bebop_default.cmake

@@ -16,6 +16,7 @@ set(config_module_list
 	# Board support modules
 	#
 	drivers/device
+	drivers/linux_sbus
 	modules/sensors
 	platforms/posix/drivers/df_ms5607_wrapper
 	platforms/posix/drivers/df_mpu6050_wrapper

cmake/configs/posix_eagle_hil.cmake

@@ -22,6 +22,7 @@ set(config_module_list
 	drivers/device
 	drivers/boards/sitl
 	drivers/led
+	drivers/linux_sbus
 
 	systemcmds/param
 	systemcmds/ver

cmake/configs/posix_rpi_common.cmake

@@ -74,6 +74,7 @@ set(config_module_list
 	#
 	# PX4 drivers
 	#
+	drivers/linux_sbus
 	drivers/gps
 	drivers/navio_adc
 	drivers/navio_sysfs_rc_in

cmake/configs/posix_sdflight_default.cmake

@@ -30,6 +30,7 @@ set(CONFIG_SHMEM "1")
 set(config_module_list
 	drivers/device
 	drivers/blinkm
+	drivers/linux_sbus
 	drivers/pwm_out_sim
 	drivers/rgbled
 	drivers/led

cmake/configs/posix_sdflight_legacy.cmake

@@ -22,6 +22,7 @@ set(CONFIG_SHMEM "1")
 set(config_module_list
 	drivers/device
 	drivers/blinkm
+	drivers/linux_sbus
 	drivers/pwm_out_sim
 	drivers/rgbled
 	drivers/led