mraa.c: fix style of lookup functions

This patch has no changes in function. It fixes three style issues
to be more readable and in line to the rest of the codebase:
- return types are declared on a separate line
- reversal of Yoda conditionals
- initialize for loop variable inside loop declaration
- Fix styling of pwm lookup doxygen

Signed-off-by: Tapani Utriainen <tapani@technexion.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

api/mraa/common.h

@@ -258,11 +258,11 @@ int mraa_i2c_lookup(const char* i2c_name);
 int mraa_spi_lookup(const char* spi_name);
 
 /**
-* Get PWM index by PWM name, board must be initialised.
-*
-* @param pwm_name: Name of PWM. Eg:PWM0
-* @return int of MRAA index for PWM or -1 if not found.
-*/
+ * Get PWM index by PWM name, board must be initialised.
+ *
+ * @param pwm_name: Name of PWM. Eg:PWM0
+ * @return int of MRAA index for PWM or -1 if not found.
+ */
 int mraa_pwm_lookup(const char* pwm_name);
 
 /**

api/mraa/common.hpp

@@ -280,12 +280,12 @@ getSpiLookup(std::string spi_name)
 }
 
 /**
-* Get PWM index by PWM name, board must be initialised.
-*
-* @param pwm_name: Name of PWM. Eg:PWM0
-* @throws std::invalid_argument if name is not found
-* @return int of MRAA index for PWM
-*/
+ * Get PWM index by PWM name, board must be initialised.
+ *
+ * @param pwm_name: Name of PWM. Eg:PWM0
+ * @throws std::invalid_argument if name is not found
+ * @return int of MRAA index for PWM
+ */
 inline int
 getPwmLookup(std::string pwm_name)
 {