Don't manually extern OPENSSL_ia32cap_P.

This probably snuck in when adapting the code from upstream. There's a header
file for it now. (Also it's uint32_t now rather than unsigned int.)

Change-Id: Ie8f45bc7a88988744174182a70512c0eff37cc1c
Reviewed-on: https://boringssl-review.googlesource.com/2441
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/cipher/e_rc4.c b/crypto/cipher/e_rc4.c
index f1d4c50..efd33d9 100644
--- a/crypto/cipher/e_rc4.c
+++ b/crypto/cipher/e_rc4.c
@@ -59,6 +59,7 @@
 #include <assert.h>
 
 #include <openssl/cipher.h>
+#include <openssl/cpu.h>
 #include <openssl/err.h>
 #include <openssl/md5.h>
 #include <openssl/mem.h>
@@ -176,7 +177,6 @@
   MD5_CTX md;
 #if defined(STITCHED_CALL)
   size_t rc4_off, md5_off, blocks;
-  extern unsigned int OPENSSL_ia32cap_P[];
 #else
   const size_t rc4_off = 0;
   const size_t md5_off = 0;