i965: Fix register types in dump_instructions(), again.

i965: Fix register types in dump_instructions(), again.

In commit e57d77280efcbfd6579a88f071426653287ef833, I fixed this for
destinations in the Vec4 backend, and sources in the scalar backend.
But not both types in both backends.

To prevent this mess from continuing, make the reg_encoding table
static, so only the disassembler can use it.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>