simd_impl.h,SIMD_TUPLE: make name param type explicit
simd_impl.h,SIMD_TUPLE: make name param type explicit

fixes an error under Xcode 8:
array initializer must be an initializer list or string literal
the type deduced from #name was e.g., char[11]

Change-Id: I6fcb29e3229db7650eee106ef6e3986515dc0a07

GrokImageCompression/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom,luctrudeau/aom,smarter/aom,smarter/aom,smarter/aom,GrokImageCompression/aom,luctrudeau/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,luctrudeau/aom,luctrudeau/aom