drivers/hwtracing: fix coresight-etm4x implicit <module.h> usage

In commit 2e1cdfe184 ("coresight-etm4x:
Adding CoreSight ETM4x driver") this driver was added.

It uses module_amba_driver() to register itself with the system,
which is just an alias for module_driver.  This currently works by
relying on getting that via init.h but we are planning to move that
code[1] to module.h -- at which time this will fail to compile since
it does not include module.h currently, resulting in:

drivers/hwtracing/coresight/coresight-etm4x.c:2701:1: note: in expansion of macro ‘module_amba_driver’
 module_amba_driver(etm4x_driver);
 ^
include/linux/device.h:1296:1: error: type defaults to ‘int’ in declaration of ‘module_init’ [-Werror=implicit-int]
 module_init(__driver##_init); \
 ^

In the future, the amba support may want to create another alias that
uses builtin_driver[2] for cases like this which are using bool Kconfig
triggers, but for now we just fix the implicit include.

[1] https://lkml.kernel.org/r/1433276168-21550-1-git-send-email-paul.gortmaker@windriver.com
[2] https://lkml.kernel.org/r/1431287385-1526-1-git-send-email-paul.gortmaker@windriver.com

Cc: Pratik Patel <pratikp@codeaurora.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-etm4x.c

@@ -15,6 +15,7 @@
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/device.h>
+#include <linux/module.h>
 #include <linux/io.h>
 #include <linux/err.h>
 #include <linux/fs.h>