Move the alignment specifier on fe1305x2 to the type

The assembly uses aligned loads for all these.

Change-Id: I76e955861c998b2acc0f176363fed04d8f30ecdd
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/98447
Commit-Queue: David Benjamin <davidben@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>

crypto/poly1305/poly1305_arm.cc

diff --git a/crypto/poly1305/poly1305_arm.cc b/crypto/poly1305/poly1305_arm.cc
index 6620d70..2011000 100644
--- a/crypto/poly1305/poly1305_arm.cc
+++ b/crypto/poly1305/poly1305_arm.cc
@@ -28,9 +28,9 @@
 
 #if defined(OPENSSL_POLY1305_NEON)
 
-typedef struct {
+struct alignas(16) fe1305x2 {
   uint32_t v[12];  // for alignment; only using 10
-} fe1305x2;
+};
 
 #define addmulmod openssl_poly1305_neon2_addmulmod
 #define blocks openssl_poly1305_neon2_blocks
@@ -169,7 +169,7 @@
   }
 }
 
-static const fe1305x2 zero alignas(16) = {0};
+static const fe1305x2 zero = {0};
 
 struct poly1305_state_st {
   fe1305x2 r, h, c, precomp[2];