libmraa: Fix compilation warnings about unsigned ints

Make better use of unsigned/signed ints, signed ints are preffered unless there
is a good reason not to.

Signed-off-by: Alexandru Timohi <alexandru.timohi@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

api/mraa/common.h

@@ -159,7 +159,7 @@ const char* mraa_get_platform_version(int platform_offset);
  * @param priority Value from typically 0 to 99
  * @return The priority value set
  */
-int mraa_set_priority(const unsigned int priority);
+int mraa_set_priority(const int priority);
 
 /** Get the version string of mraa autogenerated from git tag
  *
@@ -214,7 +214,7 @@ int mraa_get_i2c_bus_count();
  * @param i2c_bus the logical I2C bus number
  * @return I2C adapter number in sysfs. Function will return -1 on failure
  */
-int mraa_get_i2c_bus_id(unsigned int i2c_bus);
+int mraa_get_i2c_bus_id(int i2c_bus);
 
 /**
  * Get specified platform pincount, board must be initialised.

api/mraa/common.hpp

@@ -78,7 +78,7 @@ getVersion()
  * @return The priority value set
  */
 inline int
-setPriority(const unsigned int priority)
+setPriority(const int priority)
 {
     return mraa_set_priority(priority);
 }
@@ -195,7 +195,7 @@ getI2cBusCount()
  * @return I2C adapter number in sysfs. Function will return -1 on failure
  */
 inline int
-getI2cBusId(unsigned int i2c_bus)
+getI2cBusId(int i2c_bus)
 {
     return mraa_get_i2c_bus_id(i2c_bus);
 }