bsps/mips/malta: Address unused parameter warnings

Add "(void) param;" annotation to address unused parameter warnings.
Found with GCC's warning -Wunused-parameter.

bsps/mips/malta/irq/vectorisrs.c

@@ -45,6 +45,8 @@ void mips_default_isr( int vector );
 
 void mips_vector_isr_handlers( CPU_Interrupt_frame *frame )
 {
+  (void) frame;
+
   unsigned int sr;
   unsigned int cause;
   unsigned int pending;

bsps/mips/malta/pci/pci.c

@@ -981,6 +981,8 @@ void pci_memory_enable(
   unsigned char function
 )
 {
+  (void) bus;
+
   uint16_t data;
 
   pci_read_config_word(0, slot, function, PCI_COMMAND, &data);
@@ -995,6 +997,8 @@ void pci_io_enable(
   unsigned char function
 )
 {
+  (void) bus;
+
   uint16_t data;
 
   pci_read_config_word(0, slot, function, PCI_COMMAND, &data);
@@ -1008,6 +1012,8 @@ void pci_busmaster_enable(
   unsigned char function
 )
 {
+  (void) bus;
+
   uint16_t data;
 
   pci_read_config_word(0, slot, function, PCI_COMMAND, &data);

bsps/mips/malta/start/bspstart.c

@@ -122,6 +122,8 @@ void bsp_start( void )
  */
 void clear_cache( void *address, size_t n )
 {
+  (void) address;
+  (void) n;
 }
 
 void get_mem_info(