staging: ccree: fix boolreturn.cocci warning

This fixes the following coccinelle warning:
WARNING: return of 0/1 in function 'ssi_is_hw_key' with return type bool.

return "false" instead of 0.

Signed-off-by: Suniel Mahesh <sunil.m@techveda.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>