treewide: replace or remove redundant def_bool in Kconfig files

'def_bool X' is a shorthand for 'bool' plus 'default X'.

'def_bool' is redundant where 'bool' is already present, so 'def_bool X'
can be replaced with 'default X', or removed if X is 'n'.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
diff --git a/init/Kconfig b/init/Kconfig
index 8426d59c..a4b8075 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1504,7 +1504,7 @@
 
 config SGETMASK_SYSCALL
 	bool "sgetmask/ssetmask syscalls support" if EXPERT
-	def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
+	default PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
 	help
 	  sys_sgetmask and sys_ssetmask are obsolete system calls
 	  no longer supported in libc but still enabled by default in some