Hexagon (target/hexagon) Restore --disable-hexagon-idef-parser build

The --disable-hexagon-idef-parser configuration was broken by this patch
2feacf60c23ba6 (target/hexagon: Drop tcg_temp_free from C code)

That config is not tested by CI

Fix is simple: Mark a few TCGv variables as unused

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Message-Id: <20230306172515.346813-1-tsimpson@quicinc.com>

target/hexagon/gen_tcg.h

@@ -419,16 +419,16 @@
 
 #define fGEN_TCG_STORE(SHORTCODE) \
     do { \
-        TCGv HALF = tcg_temp_new(); \
-        TCGv BYTE = tcg_temp_new(); \
+        TCGv HALF G_GNUC_UNUSED = tcg_temp_new(); \
+        TCGv BYTE G_GNUC_UNUSED = tcg_temp_new(); \
         SHORTCODE; \
     } while (0)
 
 #define fGEN_TCG_STORE_pcr(SHIFT, STORE) \
     do { \
         TCGv ireg = tcg_temp_new(); \
-        TCGv HALF = tcg_temp_new(); \
-        TCGv BYTE = tcg_temp_new(); \
+        TCGv HALF G_GNUC_UNUSED = tcg_temp_new(); \
+        TCGv BYTE G_GNUC_UNUSED = tcg_temp_new(); \
         tcg_gen_mov_tl(EA, RxV); \
         gen_read_ireg(ireg, MuV, SHIFT); \
         gen_helper_fcircadd(RxV, RxV, ireg, MuV, hex_gpr[HEX_REG_CS0 + MuN]); \