command: Always pass a string to the DECL_CONSTANT() macro

Make it clear that the name of the constant being defined is a string.
When the value being defined is also a string, use a new
DECL_CONSTANT_STR() macro.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/atsamd/adc.c

@@ -37,7 +37,7 @@ static const uint8_t adc_pins[] = {
 };
 #endif
 
-DECL_CONSTANT(ADC_MAX, 4095);
+DECL_CONSTANT("ADC_MAX", 4095);
 
 static struct gpio_adc gpio_adc_pin_to_struct(uint8_t pin)
 {

src/atsamd/hard_pwm.c

@@ -41,7 +41,7 @@ static const struct gpio_pwm_info pwm_regs[] = {
 
 #define MAX_PWM 255
 
-DECL_CONSTANT(PWM_MAX, MAX_PWM);
+DECL_CONSTANT("PWM_MAX", MAX_PWM);
 
 struct gpio_pwm
 gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint8_t val)

src/atsamd/main.c

@@ -8,7 +8,7 @@
 #include "internal.h" // NVIC_SystemReset
 #include "sched.h" // sched_main
 
-DECL_CONSTANT(MCU, CONFIG_MCU);
+DECL_CONSTANT_STR("MCU", CONFIG_MCU);
 
 // Return the start of memory available for dynamic allocations
 void *