Correct name and documentation of preprocessor symbol check function

It's not remove_unset_options, it's remove_enabled_options (or
keep_disabled_options).

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/scripts/common.make b/scripts/common.make
index 6d2fbc3..2f27d0e 100644
--- a/scripts/common.make
+++ b/scripts/common.make
@@ -31,19 +31,19 @@
 WINDOWS_BUILD=1
 endif
 
-## Usage: $(call remove_unset_options,PREPROCESSOR_INPUT)
-## Remove the preprocessor symbols that are not set in the current configuration
+## Usage: $(call remove_enabled_options,PREPROCESSOR_INPUT)
+## Remove the preprocessor symbols that are set in the current configuration
 ## from PREPROCESSOR_INPUT. Also normalize whitespace.
 ## Example:
-##   $(call remove_unset_options,MBEDTLS_FOO MBEDTLS_BAR)
+##   $(call remove_set_options,MBEDTLS_FOO MBEDTLS_BAR)
 ## This expands to an empty string "" if MBEDTLS_FOO and MBEDTLS_BAR are both
-## disabled, to "MBEDTLS_FOO" if MBEDTLS_BAR is enabled but MBEDTLS_FOO is
+## enabled, to "MBEDTLS_FOO" if MBEDTLS_BAR is enabled but MBEDTLS_FOO is
 ## disabled, etc.
 ##
 ## This only works with a Unix-like shell environment (Bourne/POSIX-style shell
 ## and standard commands) and a Unix-like compiler (supporting -E). In
 ## other environments, the output is likely to be empty.
-define remove_unset_options
+define remove_enabled_options
 $(strip $(shell
   exec 2>/dev/null;
   { echo '#include <mbedtls/build_info.h>'; echo $(1); } |
@@ -66,11 +66,11 @@
   SHARED_SUFFIX=
   ifndef THREADING
     # Auto-detect configurations with pthread.
-    # If the call to remove_unset_options returns "control", the symbols
+    # If the call to remove_enabled_options returns "control", the symbols
     # are confirmed set and we link with pthread.
     # If the auto-detection fails, the result of the call is empty and
     # we keep THREADING undefined.
-    ifeq (control,$(call remove_unset_options,control MBEDTLS_THREADING_C MBEDTLS_THREADING_PTHREAD))
+    ifeq (control,$(call remove_enabled_options,control MBEDTLS_THREADING_C MBEDTLS_THREADING_PTHREAD))
       THREADING := pthread
     endif
   endif