fs/procfs/fs_procfsprogrem: Add /proc/progmem. This is an alternative way to get the information that was previoulsy available in apps/system/free. apps/system/free was removed beause it made illegal calls into the OS violating the portable interface. This new procfs entry provides the same information with no such violation.

include/nuttx/progmem.h

@@ -45,6 +45,8 @@
 
 #include <stdbool.h>
 
+#ifdef CONFIG_ARCH_HAVE_PROGMEM
+
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
@@ -207,4 +209,5 @@ ssize_t up_progmem_write(size_t addr, FAR const void *buf, size_t count);
 }
 #endif
 
+#endif /* CONFIG_ARCH_HAVE_PROGMEM */
 #endif /* __INCLUDE_NUTTX_PROGMEM_H */