demos/evp: add make clean

Add make clean for evp demos and remove whitespace from a line.

CLA: trivial
Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NPaul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/7072)

demos/evp/Makefile

@@ -11,10 +11,13 @@
 CFLAGS = $(OPENSSL_INCS_LOCATION)
 LDFLAGS = $(OPENSSL_LIBS_LOCATION) -lssl -lcrypto
 
-all: aesccm aesgcm 
+all: aesccm aesgcm
 
 aesccm: aesccm.o
 aesgcm: aesgcm.o
 
 aesccm aesgcm:
 	$(CC) $(CFLAGS) -o $@ $< $(LDFLAGS)
+
+clean:
+	$(RM) aesccm aesgcm *.o