ASoC: nau8825: drop redundant idiom when converting integer to boolean

Thanks Mark and Anatol for the discussion. According to the result,
the standard C will translate any non-zero value into true, or
false otherwise.
QUOTE:
"6.3.1.2 Boolean type
When any scalar value is converted to _Bool, the result is 0 if the
value compares equal to 0; otherwise, the result is 1
"
Thus, the "!!" idiom is removed.

Signed-off-by: John Hsu <KCHSU0@nuvoton.com>
Signed-off-by: Mark Brown <broonie@kernel.org>