Only build ssse3 filter functions on 64 bit

Avoid an unused function warning by only building the functions when
they will be used.

Change-Id: I53b5bdc5a180c79d63b34e4c8921d679bbc54009

vpx_dsp/x86/vpx_subpixel_8t_intrin_ssse3.c

diff --git a/vpx_dsp/x86/vpx_subpixel_8t_intrin_ssse3.c b/vpx_dsp/x86/vpx_subpixel_8t_intrin_ssse3.c
index 772e01e..4881758 100644
--- a/vpx_dsp/x86/vpx_subpixel_8t_intrin_ssse3.c
+++ b/vpx_dsp/x86/vpx_subpixel_8t_intrin_ssse3.c
@@ -203,6 +203,7 @@
   }
 }
 
+#if ARCH_X86_64
 static void vpx_filter_block1d16_h8_intrin_ssse3(const uint8_t *src_ptr,
                                                  ptrdiff_t src_pixels_per_line,
                                                  uint8_t *output_ptr,
@@ -319,6 +320,7 @@
     output_ptr+=output_pitch;
   }
 }
+#endif  // ARCH_X86_64
 
 void vpx_filter_block1d8_v8_intrin_ssse3(const uint8_t *src_ptr,
                                          ptrdiff_t src_pitch,
@@ -408,6 +410,7 @@
   }
 }
 
+#if ARCH_X86_64
 static void vpx_filter_block1d16_v8_intrin_ssse3(const uint8_t *src_ptr,
                                                  ptrdiff_t src_pitch,
                                                  uint8_t *output_ptr,
@@ -522,6 +525,7 @@
     output_ptr+=out_pitch;
   }
 }
+#endif  // ARCH_X86_64
 
 #if ARCH_X86_64
 filter8_1dfunction vpx_filter_block1d16_v8_intrin_ssse3;