cmd: CMD_ACPI depends on ACPIGEN

Trying to compile qemu-x86_64_defconfig with CONFIG_CMD_ACPI=y and
CONFIG_ACPIGEN=n fails with

ld.bfd: cmd/built-in.o: in function `do_acpi_items':
cmd/acpi.c:162: undefined reference to `acpi_dump_items'

Add the missing configuration dependency.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
1 file changed