[peerdist] Fix segment identifier constant on big-endian targets

The "MS_P2P_CACHING" constant (used as part of the HMAC digest
calculation for the segment identifier) is a UTF-16LE string.  On a
big-endian target, a wide-character string literal will have the wrong
endianness.

Fix by using a byte array rather than a wide-character string.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/pccrc.h

diff --git a/src/include/ipxe/pccrc.h b/src/include/ipxe/pccrc.h
index 6d0e3f1..61f5d0b 100644
--- a/src/include/ipxe/pccrc.h
+++ b/src/include/ipxe/pccrc.h
@@ -388,7 +388,9 @@
  * ASCII string.  The terminating wNUL *is* included within the
  * constant.
  */
-#define PEERDIST_SEGMENT_ID_MAGIC L"MS_P2P_CACHING"
+#define PEERDIST_SEGMENT_ID_MAGIC					\
+	{ 'M', 0, 'S', 0, '_', 0, 'P', 0, '2', 0, 'P', 0, '_', 0,	\
+	  'C', 0, 'A', 0, 'C', 0, 'H', 0, 'I', 0, 'N', 0, 'G', 0, 0, 0 }
 
 /** A content information block */
 struct peerdist_info_block {

src/net/pccrc.c

diff --git a/src/net/pccrc.c b/src/net/pccrc.c
index 4bf2f44..7ee6afe 100644
--- a/src/net/pccrc.c
+++ b/src/net/pccrc.c
@@ -106,7 +106,7 @@
 	struct digest_algorithm *digest = info->digest;
 	uint8_t ctx[ hmac_ctxsize ( digest ) ];
 	size_t digestsize = info->digestsize;
-	static const uint16_t magic[] = PEERDIST_SEGMENT_ID_MAGIC;
+	static const uint8_t magic[] = PEERDIST_SEGMENT_ID_MAGIC;
 
 	/* Sanity check */
 	assert ( digestsize <= sizeof ( segment->hash ) );