games/coffeebreak: Correct sed and patch applied twice

Last commit "Move man to share/man" I used patch to set MANDIR and sed
to fix hardcoded PREFIX=/usr/local on wrksrc Makefile.

Simplify and correct changes with use of MAKE_ARGS.
Not bumping port revision as is doesn't change build.

Reported by:	danfe
Approved by:	portmgr (blanket)
Fixes:		021fcd3 Move man pages to share/man

games/coffeebreak/Makefile

@@ -12,13 +12,13 @@ LICENSE=	BSD2CLAUSE
 USE_GITHUB=	yes
 GH_ACCOUNT=	0mp
 
+MAKE_ARGS=	MANDIR=${STAGEDIR}${PREFIX}/share/man \
+		PREFIX=${PREFIX}
+
 NO_ARCH=	yes
 NO_BUILD=	yes
 
 PLIST_FILES=	bin/coffeebreak \
 		share/man/man6/coffeebreak.6.gz
 
-post-patch:
-	${REINPLACE_CMD} 's|/usr/local|${PREFIX}|g' ${WRKSRC}/Makefile
-
 .include <bsd.port.mk>