x86: emulation: Move the x86_64 build to Q35

Q35 is newer and has a native PCI Express bus. Move to using this by
default.

Update the QEMU script to select the correct machine.

Signed-off-by: Simon Glass <sjg@chromium.org>

configs/qemu-x86_64_defconfig

@@ -6,7 +6,7 @@ CONFIG_NR_DRAM_BANKS=8
 CONFIG_ENV_SIZE=0x40000
 CONFIG_MAX_CPUS=2
 CONFIG_SPL_DM_SPI=y
-CONFIG_DEFAULT_DEVICE_TREE="qemu-x86_i440fx"
+CONFIG_DEFAULT_DEVICE_TREE="qemu-x86_q35"
 CONFIG_SPL_SYS_MALLOC_F_LEN=0x4800
 CONFIG_SPL_TEXT_BASE=0xfffd0000
 CONFIG_DEBUG_UART_BASE=0x3f8

configs/qemu-x86_defconfig

@@ -5,7 +5,7 @@ CONFIG_BLOBLIST_SIZE_RELOC=0x40000
 CONFIG_NR_DRAM_BANKS=8
 CONFIG_ENV_SIZE=0x40000
 CONFIG_MAX_CPUS=2
-CONFIG_DEFAULT_DEVICE_TREE="qemu-x86_i440fx"
+CONFIG_DEFAULT_DEVICE_TREE="qemu-x86_q35"
 CONFIG_DEBUG_UART_BASE=0x3f8
 CONFIG_DEBUG_UART_CLOCK=1843200
 CONFIG_DEBUG_UART=y

scripts/build-qemu

@@ -151,6 +151,7 @@ class BuildQemu:
             self.board = 'qemu-x86'
             default_bios = 'u-boot.rom'
             self.qemu = 'qemu-system-i386'
+            self.qemu_extra.extend(['-machine', 'q35'])
             if self.helper.bitness == 64:
                 self.board = 'qemu-x86_64'
                 self.qemu = 'qemu-system-x86_64'