Move MBEDTLS_ERR_xxx Doxygen comments before the definition

Now that descriptions of error codes no longer have to be on the same line
for the sake of generate_errors.pl, move them to their own line before the
definition. This aligns them with what we do for other definitions, and
means that we no longer need to have very long lines containing both the C
definition and the comment.

```
perl -i -pe 's~^(#define +MBEDTLS_ERR_\w+ +-\w+) */\*[*!]<(.*)\*/~/**$2*/\n$1~' include/mbedtls/*.h
```

This commit does not change the output of generate_errors.pl.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/entropy.h b/include/mbedtls/entropy.h
index fa0b24f..d6ad8e7 100644
--- a/include/mbedtls/entropy.h
+++ b/include/mbedtls/entropy.h
@@ -48,11 +48,16 @@
 #include "mbedtls/havege.h"
 #endif
 
-#define MBEDTLS_ERR_ENTROPY_SOURCE_FAILED                 -0x003C  /**< Critical entropy source failure. */
-#define MBEDTLS_ERR_ENTROPY_MAX_SOURCES                   -0x003E  /**< No more sources can be added. */
-#define MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED            -0x0040  /**< No sources have been added to poll. */
-#define MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE              -0x003D  /**< No strong sources have been added to poll. */
-#define MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR                 -0x003F  /**< Read/write error in file. */
+/** Critical entropy source failure. */
+#define MBEDTLS_ERR_ENTROPY_SOURCE_FAILED                 -0x003C
+/** No more sources can be added. */
+#define MBEDTLS_ERR_ENTROPY_MAX_SOURCES                   -0x003E
+/** No sources have been added to poll. */
+#define MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED            -0x0040
+/** No strong sources have been added to poll. */
+#define MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE              -0x003D
+/** Read/write error in file. */
+#define MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR                 -0x003F
 
 /**
  * \name SECTION: Module settings