The definition of BRCMF_EVENTING_MASK_LEN results in a sparse
error message

.../fweh.c:331:22: error: bad constant expression
.../fweh.c:388:22: error: bad constant expression
.../dhd_common.c:256:22: error: bad constant expression

This is caused by the use of roundup() in BRCMF_EVENTING_MASK_LEN
and it is used to allocate an array variable on the stack. Better
use DIV_ROUND_UP() macro.
Reviewed-by: NFranky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: NHante Meuleman <meuleman@broadcom.com>
Reviewed-by: NPieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: NArend van Spriel <arend@broadcom.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>