cmd: qfw: rename qemu_fw_cfg.[c|h] to qfw.[c|h]

Make file names consistent with CONFIG_QFW and CONFIG_CMD_QFW

Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 08b761f..c5a7a59 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -593,7 +593,7 @@
 	     sound init   - set up sound system
 	     sound play   - play a sound
 
-config CMD_QEMU_FW_CFG
+config CMD_QFW
 	bool "qfw"
 	depends on X86
 	select QFW