mips: sibyte: add missing MODULE_DESCRIPTION() macro

Since commit 1fffe7a3 ("script: modpost: emit a warning when the
description is missing"), a module without a MODULE_DESCRIPTION() will
result in a warning with make W=1. The following warning is being
observed when ARCH=mips and CONFIG_SIBYTE_TBPROF=m:

WARNING: modpost: missing MODULE_DESCRIPTION() in arch/mips/sibyte/common/sb_tbprof.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>