build: Remove libusb dependency in Linux

As the last user, the CSR support code, was removed.

configure.ac

@@ -199,7 +199,6 @@ AC_SUBST(BACKEND, "$with_backend")
 have_idevice=no
 if test x$with_backend = xlinux; then
 	PKG_CHECK_MODULES(GUDEV, [gudev-1.0 >= 147])
-	PKG_CHECK_MODULES(USB, [libusb-1.0 >= 1.0.0])
 	AC_ARG_WITH(idevice, AS_HELP_STRING([--without-idevice],[Build without libimobiledevice]),
 		    with_idevice=$withval,with_idevice=yes)
 	LIBPLIST_DEP=libplist

src/Makefile.am

@@ -69,7 +69,6 @@ upowerd_CPPFLAGS =						\
 
 upowerd_LDADD =							\
 	-lm							\
-	$(USB_LIBS)						\
 	$(GIO_LIBS)						\
 	$(GIO_UNIX_LIBS)					\
 	$(UPOWER_LIBS)
@@ -94,7 +93,6 @@ endif
 if BACKEND_TYPE_LINUX
 upowerd_LDADD += 						\
 	linux/libupshared.la					\
-	$(USB_LIBS)						\
 	$(GUDEV_LIBS)						\
 	$(IDEVICE_LIBS)						\
 	$(NULL)

src/linux/Makefile.am

@@ -7,7 +7,6 @@ AM_CPPFLAGS = \
 	-DG_LOG_DOMAIN=\"UPower-Linux\"				\
 	-DPACKAGE_SYSCONF_DIR=\""$(sysconfdir)"\"		\
 	-I$(top_srcdir)/libupower-glib				\
-	$(USB_CFLAGS)						\
 	$(GIO_CFLAGS)						\
 	$(GIO_UNIX_CFLAGS)					\
 	$(GUDEV_CFLAGS)						\