x86: Add platform directory

x86 has finally arrived in the embedded nightmare and will rapidly
grow SoC platform support in various flavours. So we need a place for
the platform support files. That also allows us to clean up the
dumpground which arch/x86/kernel has become over time.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/Kbuild

@@ -14,3 +14,4 @@ obj-y += crypto/
 obj-y += vdso/
 obj-$(CONFIG_IA32_EMULATION) += ia32/
 
+obj-y += platform/