tpm_tis: make array cmd_getticks static const to shrink object code size

Don't populate array cmd_getticks on the stack, instead make it static
const.  Makes the object code smaller by over 160 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  18813	   3152	    128	  22093	   564d	drivers/char/tpm/tpm_tis_core.o

After:
   text	   data	    bss	    dec	    hex	filename
  18554	   3248	    128	  21930	   55aa	drivers/char/tpm/tpm_tis_core.o

Cc: stable@vger.kernel.org
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>