sysutils/firmware/bwfm: Use EXTRACT_FILES

Although it is designed for one file in DISTFILES only, it can still
be used if the glob(7) patterns match all files, i.e. none of the
extractions fail due to unmatched patterns.

Cuts WRKDIR from ~450M to ~18M.

OK?

Index: Makefile
===================================================================
RCS file: /cvs/ports/sysutils/firmware/bwfm/Makefile,v
retrieving revision 1.7
diff -u -p -r1.7 Makefile
--- Makefile 17 Jun 2020 21:48:16 -0000 1.7
+++ Makefile 27 Mar 2021 17:07:36 -0000
@@ -8,6 +8,8 @@ DISTNAME= linux-firmware-${LINUX_VER}
EXTRACT_SUFX= .tar.xz
DISTFILES= ${DISTNAME}${EXTRACT_SUFX} \
brcm-supplemental-${SUP_VER}.tar.gz:1
+# broad enough to reduce WRKSRC size but specific enough to match both DISTFILES
+EXTRACT_FILES= \*/{brcm\*.{bin,txt},LICEN[CS]E\*}

MAINTAINER= Patrick Wildt <patrick@blueri.se>