uboot-imx

x86: qemu: re-structure qemu_fwcfg_list_firmware()

Re-write the logic in qemu_fwcfg_list_firmware(), add a function
qemu_fwcfg_read_firmware_list() to handle reading firmware list.

Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>