x86: qemu: rename qemu/acpi_table.c

Rename qemu/acpi_table.c to qemu/e820.c, because ACPI stuff is moved
to qfw core, this file only contains code for installing e820 table.

Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/cpu/qemu/Makefile b/arch/x86/cpu/qemu/Makefile
index 7c08c3d..a080c5e 100644
--- a/arch/x86/cpu/qemu/Makefile
+++ b/arch/x86/cpu/qemu/Makefile
@@ -8,5 +8,4 @@
 obj-y += car.o dram.o
 endif
 obj-y += qemu.o
-obj-$(CONFIG_QFW) += cpu.o
-obj-$(CONFIG_GENERATE_ACPI_TABLE) += acpi_table.o
+obj-$(CONFIG_QFW) += cpu.o e820.o