intel-x86-32.conf: add common MACHINE for x86 (32-bit) BOARDS

User need to specify board value to ZEPHYR_BOARD in local.conf
ZEPHYR_BOARD = "minnowboard"

By default it set to MinnowBoard Max 'minnowboard'

Currently 32-bit supported boards:
* up_squared_32
* minnowboard

Ref:
https://docs.zephyrproject.org/latest/boards/x86/index.html



Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>

conf/machine/include/tune-core2-common.inc

+DEFAULTTUNE ?= "core2-32"
+require conf/machine/include/tune-core2.inc
+require conf/machine/include/x86-base.inc
+
+# Add x86 to MACHINEOVERRIDES
+MACHINEOVERRIDES =. "x86:"

conf/machine/intel-x86-32.conf

+#@TYPE: Machine
+#@NAME: intel-x86-32
+#@DESCRIPTION: common MACHINE for 32-bit x86 boards. User must set ${ZEPHYR_BOARD}. By default is set to 'minnowboard' board.
+
+require conf/machine/include/tune-core2-common.inc
+
+ARCH_intel-x86-32 = "x86"
+
+# Supported Boards:
+# ZEPHYR_BOARD ?= "minnowboard"
+# ZEPHYR_BOARD ?= "up_squared_32"
+ZEPHYR_BOARD ?= "minnowboard"