i965: call next_insn() before referencing a instruction by index

i965: call next_insn() before referencing a instruction by index

A single next_insn may change the base address of instruction store
memory(p->store), so call it first before referencing the instruction
store pointer from an index.

This the final prepare work to enable the dynamic store size.

v2: comments from Ken, define emit_endif as bool type

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>