samples: seccomp: turn CONFIG_SAMPLE_SECCOMP into a bool option

The prompt of CONFIG_SAMPLE_SECCOMP claims this is "loadable module
only", which is invalid.

samples/seccomp/ only contains host programs, so having it tristate
is pointless.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/samples/Kconfig b/samples/Kconfig
index d19754c..b98a763 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -103,8 +103,8 @@
 	  See also Documentation/connector/connector.txt
 
 config SAMPLE_SECCOMP
-	tristate "Build seccomp sample code -- loadable modules only"
-	depends on SECCOMP_FILTER && m
+	bool "Build seccomp sample code"
+	depends on SECCOMP_FILTER
 	help
 	  Build samples of seccomp filters using various methods of
 	  BPF filter construction.