sys: util: force Zephyr BIT/MIN/MAX/CLAMP definitions

We've been guarding the definition of BIT/MIN/MAX/CLAMP macros as they
are commonly found in other projects. This is dangerous, because
depending on the order of includes, Zephyr code could end up using
macros defined by other projects (e.g. via HALs).

The current #ifndef _protection_ goes against the recently established
guidelines in #51963, so let's remove it.

Ref.
https://docs.zephyrproject.org/latest/contribute/coding_guidelines/
index.html#rule-a-3-macro-name-collisions

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

include/zephyr/sys/util.h

@@ -250,7 +250,6 @@ extern "C" {
 #define ceiling_fraction(numerator, divider) \
 	(((numerator) + ((divider) - 1)) / (divider))
 
-#ifndef MAX
 /**
  * @brief Obtain the maximum of two values.
  *
@@ -263,9 +262,7 @@ extern "C" {
  * @returns Maximum value of @p a and @p b.
  */
 #define MAX(a, b) (((a) > (b)) ? (a) : (b))
-#endif
 
-#ifndef MIN
 /**
  * @brief Obtain the minimum of two values.
  *
@@ -278,9 +275,7 @@ extern "C" {
  * @returns Minimum value of @p a and @p b.
  */
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
-#endif
 
-#ifndef CLAMP
 /**
  * @brief Clamp a value to a given range.
  *
@@ -294,7 +289,6 @@ extern "C" {
  * @returns Clamped value.
  */
 #define CLAMP(val, low, high) (((val) <= (low)) ? (low) : MIN(val, high))
-#endif
 
 /**
  * @brief Checks if a value is within range.

include/zephyr/sys/util_macro.h

@@ -33,7 +33,6 @@ extern "C" {
  */
 #include <zephyr/sys/util_internal.h>
 
-#ifndef BIT
 #if defined(_ASMLANGUAGE)
 #define BIT(n)  (1 << (n))
 #else
@@ -43,7 +42,6 @@ extern "C" {
  */
 #define BIT(n)  (1UL << (n))
 #endif
-#endif
 
 /** @brief 64-bit unsigned integer with bit position @p _n set. */
 #define BIT64(_n) (1ULL << (_n))