[sw,pentest] Explicitely mark two functions as OT_USED

Those functions are called from assembly and will be discarded otherwise.

Signed-off-by: Amaury Pouly <[email protected]>

sw/device/tests/penetrationtests/firmware/fi/ibex_fi.c

@@ -151,6 +151,7 @@ OT_SECTION(".data")
 static volatile uint32_t sram_main_buffer[256];
 
 // Make sure that this function does not get optimized by the compiler.
+OT_USED
 void increment_counter(void) __attribute__((optnone)) {
   asm volatile("addi x5, x5, 1");
 }
@@ -334,6 +335,7 @@ static inline void read_temp_regs(uint32_t buffer[]) {
 }
 
 // Make sure that this function does not get optimized by the compiler.
+OT_USED
 void not_increment_counter(void) __attribute__((optnone)) {
   asm volatile("ret");
   asm volatile(ADDI10);