compat/bswap.h: simplify MSVC endianness detection

Modern MSVC or Windows versions don't support big-endian, so it's
unnecessary to consider architectures when using it.

This also makes ARM64 MSVC builds succeed.

Helped-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Daniel Gurney <dgurney99@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/bswap.h

@@ -74,7 +74,7 @@ static inline uint64_t git_bswap64(uint64_t x)
 }
 #endif
 
-#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
+#elif defined(_MSC_VER)
 
 #include <stdlib.h>