hw/loongarch/virt: Remove unused assignment

There is abuse usage about local variable gap. Remove
duplicated assignment and solve Coverity reported error.

Resolves: Coverity CID 1546441
Fixes: 3cc451cbce ("hw/loongarch: Refine fwcfg memory map")
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20240612033637.167787-1-maobibo@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>
1 file changed