Add .type, .hidden, and .size to the new fiat ADX assembly

.type seems to be needed for the unwind tester to report symbols
correctly. I assume it does other useful things. .hidden
(.private_extern on macOS) keeps it from being exported out of shared
libraries. I'm not positive what .size does, but if ELF wants to know
the size of the function, we should probably tell it that.

Change-Id: Iaa2e4f8a72e81092ec1d81ee2177504c7dc89c76
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/60465
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Andres Erbsen <andreser@google.com>
Reviewed-by: Adam Langley <agl@google.com>
Auto-Submit: David Benjamin <davidben@google.com>

third_party/fiat/asm/fiat_curve25519_adx_mul.S

@@ -1,8 +1,11 @@
 .text
 #if defined(__APPLE__)
+.private_extern fiat_curve25519_adx_mul
 .global _fiat_curve25519_adx_mul
 _fiat_curve25519_adx_mul:
 #else
+.type fiat_curve25519_adx_mul, @function
+.hidden fiat_curve25519_adx_mul
 .global fiat_curve25519_adx_mul
 fiat_curve25519_adx_mul:
 #endif
@@ -153,3 +156,6 @@ mov r15, [ rsp - 0x58 ]
 mov rbp, [rsp - 0x08]
 ret
 .cfi_endproc
+#if defined(__ELF__)
+.size fiat_curve25519_adx_mul, .-fiat_curve25519_adx_mul
+#endif

third_party/fiat/asm/fiat_curve25519_adx_square.S

@@ -1,8 +1,11 @@
 .text
 #if defined(__APPLE__)
+.private_extern fiat_curve25519_adx_square
 .global _fiat_curve25519_adx_square
 _fiat_curve25519_adx_square:
 #else
+.type fiat_curve25519_adx_square, @function
+.hidden fiat_curve25519_adx_square
 .global fiat_curve25519_adx_square
 fiat_curve25519_adx_square:
 #endif
@@ -121,3 +124,6 @@ mov r15, [ rsp - 0x58 ]
 mov rbp, [rsp - 0x08]
 ret
 .cfi_endproc
+#if defined(__ELF__)
+.size fiat_curve25519_adx_square, .-fiat_curve25519_adx_square
+#endif