Remove lib/libspl/include/sys/frame.h

The functionality provided by this header is not required by any
of the ZFS user space code.  Minimal functionality was provided
in commit c28a677 which added include/sys/frame.h.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #6960 
Closes #6972

lib/libspl/include/sys/Makefile.am

@@ -16,7 +16,6 @@ libspl_HEADERS = \
 	$(top_srcdir)/lib/libspl/include/sys/errno.h \
 	$(top_srcdir)/lib/libspl/include/sys/feature_tests.h \
 	$(top_srcdir)/lib/libspl/include/sys/file.h \
-	$(top_srcdir)/lib/libspl/include/sys/frame.h \
 	$(top_srcdir)/lib/libspl/include/sys/int_limits.h \
 	$(top_srcdir)/lib/libspl/include/sys/int_types.h \
 	$(top_srcdir)/lib/libspl/include/sys/inttypes.h \