i965/vs: Combine code generation's inst->opcode switch statements.

i965/vs: Combine code generation's inst->opcode switch statements.

vec4_visitor::generate_code() switches on vec4_instruction::opcode and
calls into the brw_eu_emit.c layer to generate code for some of them.
It then has a default case which calls generate_vec4_instruction() to
handle the rest...which switches on opcode and handles the rest of the
cases.

The split apparently is that generate_code() handles the actual hardware
opcodes (BRW_OPCODE_*) while generate_vec4_instruction() handles the
virtual opcodes (SHADER_OPCODE_* and VS_OPCODE_*).  But this looks
fairly arbitrary, and it makes more sense to combine the two switches.

This patch moves the cases from generate_code() into the helper function
so that generate_code() isn't as large.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>