Make use of the sizeof_field() helper instead of an open-coded version.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200527133942.GA10408@embeddedorSigned-off-by: Geert Uytterhoeven <geert@linux-m68k.org>