x86/kexec: Cleanup KEXEC_VERIFY_SIG Kconfig help text

Fix typos and also make it simpler without losing the gist of what it says.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Link: http://lkml.kernel.org/r/1426251877-11415-1-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/Kconfig

@@ -1742,14 +1742,11 @@ config KEXEC_VERIFY_SIG
 	depends on KEXEC_FILE
 	---help---
 	  This option makes kernel signature verification mandatory for
-	  kexec_file_load() syscall. If kernel is signature can not be
-	  verified, kexec_file_load() will fail.
+	  the kexec_file_load() syscall.
 
-	  This option enforces signature verification at generic level.
-	  One needs to enable signature verification for type of kernel
-	  image being loaded to make sure it works. For example, enable
-	  bzImage signature verification option to be able to load and
-	  verify signatures of bzImage. Otherwise kernel loading will fail.
+	  In addition to that option, you need to enable signature
+	  verification for the corresponding kernel image type being
+	  loaded in order for this to work.
 
 config KEXEC_BZIMAGE_VERIFY_SIG
 	bool "Enable bzImage signature verification support"