kernel: Add intel_idle driver to x86_64 build

This driver supports CPU-specific idle features on recent Intel
processors.  It does not conflict with the ACPI idle driver and
that driver will continue to be used for unsupported and non-Intel
processors.

Signed-off-by: Michael Marley <michael@michaelmarley.com>

target/linux/x86/64/config-default

@@ -182,6 +182,7 @@ CONFIG_HYPERV_UTILS=y
 # CONFIG_I7300_IDLE is not set
 # CONFIG_IA32_EMULATION is not set
 CONFIG_ILLEGAL_POINTER_VALUE=0xdead000000000000
+CONFIG_INTEL_IDLE=y
 # CONFIG_INTEL_IPS is not set
 # CONFIG_INTEL_MENLOW is not set
 # CONFIG_INTEL_MIC_BUS is not set