Rename ecp_internal.h to ecp_alt.h

This gives it a more descriptive name and indicates to alt developers
that the definitions inside are not fully internal and are available
to alt developers for use.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
diff --git a/library/ecp.c b/library/ecp.c
index ac17ff1..55d7281 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -97,7 +97,7 @@
 #define mbedtls_free       free
 #endif
 
-#include "ecp_internal.h"
+#include "ecp_alt.h"
 
 #if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
 #if defined(MBEDTLS_HMAC_DRBG_C)
diff --git a/library/ecp_internal.h b/library/ecp_alt.h
similarity index 99%
rename from library/ecp_internal.h
rename to library/ecp_alt.h
index 6a47a8f..6b1b29f 100644
--- a/library/ecp_internal.h
+++ b/library/ecp_alt.h
@@ -1,5 +1,5 @@
 /**
- * \file ecp_internal.h
+ * \file ecp_alt.h
  *
  * \brief Function declarations for alternative implementation of elliptic curve
  * point arithmetic.
@@ -293,5 +293,5 @@
 
 #endif /* MBEDTLS_ECP_INTERNAL_ALT */
 
-#endif /* ecp_internal.h */
+#endif /* ecp_alt.h */