regulator: da903x: don't build with clang

regulator: da903x: don't build with clang

The da903x driver produces an annoying false-positive warning
when built with clang:

drivers/regulator/da903x.c:395:2: error: division by zero is undefined [-Werror,-Wdivision-by-zero]
        DA9030_LDO(13, 2100, 2100, 0, INVAL, 0, 0, RCTL11, 3), /* fixed @2.1V */
        ^                          ~
drivers/regulator/da903x.c:359:2: note: expanded from macro 'DA9030_LDO'
        DA903x_LDO(DA9030, _id, min, max, step, vreg, shift, nbits, ereg, ebit)
        ^                                 ~~~~
drivers/regulator/da903x.c:320:39: note: expanded from macro 'DA903x_LDO'
                .n_voltages = (step) ? ((max - min) / step + 1) : 1,    \
                                                    ^ ~~~~
drivers/regulator/da903x.c:415:2: error: division by zero is undefined [-Werror,-Wdivision-by-zero]
        DA9034_LDO(5, 3100, 3100, 0, INVAL, 0, 0, OVER3, 7), /* fixed @3.1V */
        ^                         ~
drivers/regulator/da903x.c:356:2: note: expanded from macro 'DA9034_LDO'
        DA903x_LDO(DA9034, _id, min, max, step, vreg, shift, nbits, ereg, ebit)
        ^                                 ~~~~
drivers/regulator/da903x.c:320:39: note: expanded from macro 'DA903x_LDO'
                .n_voltages = (step) ? ((max - min) / step + 1) : 1,    \
                                                    ^ ~~~~

I already reported this as a bug in clang, but it may take a
while to fix it. As I have not been able to come up with any
reasonable workaround, I would just disable compilation here.

Link: https://bugs.llvm.org/show_bug.cgi?id=38789
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Mark Brown <broonie@kernel.org>