cs5535-mfgpt: Fix quotation marks

Commit "cs5535-mfgpt: Add another reset method" introduced an unterminated
string and broke the build.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>