target/loongarch: Clean up local variable shadowing

target/loongarch: Clean up local variable shadowing

Fix:

  [1839/2601] Compiling C object libqemu-loongarch64-softmmu.fa.p/hw_loongarch_virt.c.o
  ../hw/loongarch/virt.c: In function 'loongarch_irq_init':
  ../hw/loongarch/virt.c:665:14: warning: declaration of 'i' shadows a previous local [-Wshadow=compatible-local]
       for (int i = 0; i < num; i++) {
                ^
  ../hw/loongarch/virt.c:582:19: note: shadowed declaration is here
       int cpu, pin, i, start, num;

Signed-off-by: Song Gao <gaosong@loongson.cn>
Message-ID: <20230926071253.3601021-1-gaosong@loongson.cn>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>