r300/compiler: Move declaration before code.

r300/compiler: Move declaration before code.

Fixes these GCC warnings on linux-x86 build.
r500_fragprog_emit.c: In function ‘emit_paired’:
r500_fragprog_emit.c:237: warning: ISO C90 forbids mixed declarations and code
r500_fragprog_emit.c: In function ‘emit_tex’:
r500_fragprog_emit.c:367: warning: ISO C90 forbids mixed declarations and code
r500_fragprog_emit.c: In function ‘emit_flowcontrol’:
r500_fragprog_emit.c:415: warning: ISO C90 forbids mixed declarations and code
r500_fragprog_emit.c: In function ‘r500BuildFragmentProgramHwCode’:
r500_fragprog_emit.c:633: warning: ISO C90 forbids mixed declarations and code