Fix initialisers in dct-test.c.

Silences a warning when running fate on unusual platforms:
libavcodec/dct-test.c:101:21: warning: missing braces around initializer [-Wmissing-braces]
libavcodec/dct-test.c:101:21: warning: (near initialization for 'fdct_tab_arch[0]') [-Wmissing-braces]
libavcodec/dct-test.c:102:21: warning: missing braces around initializer [-Wmissing-braces]
libavcodec/dct-test.c:102:21: warning: (near initialization for 'idct_tab_arch[0]') [-Wmissing-braces]

libavcodec/dct-test.c

@@ -98,8 +98,8 @@ static const struct algo idct_tab[] = {
 #elif ARCH_X86
 #include "x86/dct-test.c"
 #else
-static const struct algo fdct_tab_arch[] = { 0 };
-static const struct algo idct_tab_arch[] = { 0 };
+static const struct algo fdct_tab_arch[] = { { 0 } };
+static const struct algo idct_tab_arch[] = { { 0 } };
 #endif
 
 #define AANSCALE_BITS 12