media: drx-k: remove unused MulDiv32 function

This function has never been used. Found with clang:

drivers/media/dvb-frontends/drxk_hard.c:159:19: warning: unused function 'MulDiv32' [-Wunused-function]
static inline u32 MulDiv32(u32 a, u32 b, u32 c)

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>