build.sh: set device from sdmmc to sd for defconfig #355

Job	Run time
build (bpi-r3, sdmmc emmc spi-nand spi-nor, true)	5m 58s
build (bpi-r4lite, sdmmc emmc spi-nand, true)	5m 20s
build (bpi-r2pro, sdmmc emmc, false)	2m 44s
build (bpi-r4, sdmmc emmc spi-nand, true)	5m 0s
build (bpi-r2, sdmmc, false)	2m 8s
build (bpi-r64, sdmmc emmc, true)	4m 28s
build (bpi-r3mini, emmc spi-nand, true)	3m 24s
build (bpi-r4pro, sdmmc emmc spi-nand, true)	5m 38s
	34m 40s

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