score: Require power of two CPU_STACK_MINIMUM_SIZE

For most CPU ports this was already the case.  This makes it possible to use
the size as an object alignment using RTEMS_ALIGNED().

cpukit/score/cpu/aarch64/include/rtems/score/cpu.h

@@ -102,7 +102,7 @@
 
 #define CPU_PROVIDES_ISR_IS_IN_PROGRESS FALSE
 
-#define CPU_STACK_MINIMUM_SIZE (1024 * 10)
+#define CPU_STACK_MINIMUM_SIZE (1024 * 8)
 
 /* This could be either 4 or 8, depending on the ABI in use.
  * Could also use __LP64__ or __ILP32__ */

cpukit/score/cpu/moxie/include/rtems/score/cpu.h

@@ -228,7 +228,7 @@ typedef struct {
  *
  *  XXX
  */
-#define CPU_STACK_MINIMUM_SIZE          (1536)
+#define CPU_STACK_MINIMUM_SIZE          (2048)
 
 /**
  * Size of a pointer.

cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h

@@ -554,7 +554,8 @@ extern Context_Control_fp _CPU_Null_fp_context;
  * @addtogroup RTEMSScoreCPUExampleContext
  * 
  * Should be large enough to run all RTEMS tests.  This ensures
- * that a "reasonable" small application should not have any problems.
+ * that a "reasonable" small application should not have any problems.  The
+ * size shall be a power of two.
  *
  * Port Specific Information:
  *

cpukit/score/src/percpuasm.c

@@ -44,7 +44,7 @@
 #include <rtems/score/percpu.h>
 
 #define PER_CPU_IS_POWER_OF_TWO( value ) \
-  ( ( ( ( value ) - 1 ) & ( value ) ) == 0 )
+  ( ( value ) > 1 && ( ( ( value ) - 1 ) & ( value ) ) == 0 )
 
 /*
  * The minimum alignment of two is due to the Heap Handler which uses the
@@ -72,6 +72,11 @@ RTEMS_STATIC_ASSERT(
   CPU_STACK_ALIGNMENT
 );
 
+RTEMS_STATIC_ASSERT(
+  PER_CPU_IS_POWER_OF_TWO( CPU_STACK_MINIMUM_SIZE ),
+  CPU_STACK_MINIMUM_SIZE
+);
+
 RTEMS_STATIC_ASSERT(
   sizeof(void *) == CPU_SIZEOF_POINTER,
   CPU_SIZEOF_POINTER