Use strings such as "hw" or "sw" to indicate the type of error injection
to be performed.

Current flags attribute derives the meanings of values that can be
programmed into it from asm/mce.h. Moving to defined strings for the
attribute allows this module to be self-sufficient and removes the
dependency. Also, we can introduce new flags as and when needed without
having to worry about conflicting with the flags already defined in
asm/mce.h.

Also, modify do_inject() to use the newly defined injection_type enum to
figure out the injection mechanism we need to use
Suggested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: mchehab@osg.samsung.com
Cc: x86-ml <x86@kernel.org>
Link: http://lkml.kernel.org/r/1433277362-10911-4-git-send-email-Aravind.Gopalakrishnan@amd.com
[ Use strstrip() return value. ]
Signed-off-by: Borislav Petkov <bp@suse.de>