Add missing boringssl_prefix_symbols_asm.h include.

This file probably should be switched to perlasm, but this is an easier fix for
now. It touches ymm registers, so Windows will be a little fussy.

Change-Id: I7b89435cb5c3e908b3bc784d7c305f115e707358
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/38864
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>

crypto/hrss/asm/poly_rq_mul.S

diff --git a/crypto/hrss/asm/poly_rq_mul.S b/crypto/hrss/asm/poly_rq_mul.S
index d384627..835d716 100644
--- a/crypto/hrss/asm/poly_rq_mul.S
+++ b/crypto/hrss/asm/poly_rq_mul.S
@@ -14,6 +14,10 @@
 
 #if !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_SMALL) && defined(__linux__)
 
+#if defined(BORINGSSL_PREFIX)
+#include <boringssl_prefix_symbols_asm.h>
+#endif
+
 // This is the polynomial multiplication function from [HRSS], provided by kind
 // permission of the authors.
 //