nvme: Add nvme commands

Add nvme commands in U-Boot command line.

1. "nvme scan" - scan NVMe blk devices
2. "nvme list" - show all available NVMe blk devices
3. "nvme info" - show current or a specific NVMe blk device
4. "nvme device" - show or set current device
5. "nvme part" - print partition table
6. "nvme read" - read data from NVMe blk device
7. "nvme write" - write data to NVMe blk device

Signed-off-by: Zhikang Zhang <zhikang.zhang@nxp.com>
Signed-off-by: Wenbin Song <wenbin.song@nxp.com>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 183f932..42d955c 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -773,6 +773,13 @@
 
 endif # CMD_NAND
 
+config CMD_NVME
+	bool "nvme"
+	depends on NVME
+	default y if NVME
+	help
+	  NVM Express device support
+
 config CMD_MMC_SPI
 	bool "mmc_spi - Set up MMC SPI device"
 	help