Clean up some SSE instruction format definitions on x86-64

Clean up some SSE instruction format definitions on x86-64

Remove the instruction formats for some SSE instructions with 8 bit
immediate data, instead make some other formats optionally have an
immediate field.

This makes it necessary to move the default printer definition for
these formats into the SSE shuffle instructions. They were the only
users of these formats that didn't have a printer defined anyway.