Makefile: remove a duplicated line

There are two duplicated lines for 'make RECORDMCOUNT_WARN=1 [targets]'
in 'make help', remove the second one.
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Makefile

@@ -1296,7 +1296,6 @@ help:
 	@echo  '		2: warnings which occur quite often but may still be relevant'
 	@echo  '		3: more obscure warnings, can most likely be ignored'
 	@echo  '		Multiple levels can be combined with W=12 or W=123'
-	@echo  '  make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
 	@echo  ''
 	@echo  'Execute "make" or "make all" to build all targets marked with [*] '
 	@echo  'For further info see the ./README file'