[media] smiapp: Fix BUG_ON() on an impossible condition

[media] smiapp: Fix BUG_ON() on an impossible condition

internal_csi_format_idx and csi_format_idx are unsigned integers,
therefore they can never be nevative.
CC      drivers/media/i2c/smiapp/smiapp-core.o
In file included from include/linux/err.h:4:0,
                 from include/linux/clk.h:15,
                 from drivers/media/i2c/smiapp/smiapp-core.c:29:
drivers/media/i2c/smiapp/smiapp-core.c: In function ‘smiapp_update_mbus_formats’:
include/linux/kernel.h:669:20: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
 #define min(x, y) ({    \
                    ^
include/linux/compiler.h:153:42: note: in definition of macro ‘unlikely’
 # define unlikely(x) __builtin_expect(!!(x), 0)
                                          ^
drivers/media/i2c/smiapp/smiapp-core.c:402:2: note: in expansion of macro ‘BUG_ON’
  BUG_ON(min(internal_csi_format_idx, csi_format_idx) < 0);
  ^
drivers/media/i2c/smiapp/smiapp-core.c:402:9: note: in expansion of macro ‘min’
  BUG_ON(min(internal_csi_format_idx, csi_format_idx) < 0);
         ^

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>