linuxkpi: Add <linux/cc_platform.h>

It defines the `cc_platform_has()` function.

Reviewed by:	manu
Approved by:	manu
Differential Revision:	https://reviews.freebsd.org/D38596

sys/compat/linuxkpi/common/include/linux/cc_platform.h

@@ -0,0 +1,17 @@
+/* Public domain. */
+
+#ifndef _LINUXKPI_LINUX_CC_PLATFORM_H_
+#define	_LINUXKPI_LINUX_CC_PLATFORM_H_
+
+enum cc_attr {
+	CC_ATTR_MEM_ENCRYPT,
+};
+
+static inline bool
+cc_platform_has(enum cc_attr attr __unused)
+{
+
+	return (false);
+}
+
+#endif /* _LINUXKPI_LINUX_CC_PLATFORM_H_ */