ASoC: pcm1681/pcm1791: fix typo in declaration

gcc -Wextra warns about an obvious but harmless typo in the
pcm1681_writeable_reg function, which has an extra 'register
keyword', and in pcm179x, which has a second copy of that
declaration:

sound/soc/codecs/pcm1681.c:76:42: error: 'register' is not at beginning of declaration [-Werror=old-style-declaration]
sound/soc/codecs/pcm179x.c:62:42: error: 'register' is not at beginning of declaration [-Werror=old-style-declaration]

For consistency with the rest of the file, I'm changing this from
'unsigned register' to 'unsigned int', which has the same meaning
but causes no warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mark Brown <broonie@kernel.org>