phy: cadence-torrent: Constify struct cdns_torrent_vals

'struct cdns_torrent_vals' is not modified in this driver.

Constifying this structure moves some data to a read-only section, so
increase overall security.

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
  92234	   6078	     16	  98328	  18018	drivers/phy/cadence/phy-cadence-torrent.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
  93578	   4798	     16	  98392	  18058	drivers/phy/cadence/phy-cadence-torrent.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/d9d135ee9b806726766a1bc5e1404267939aa637.1720718240.git.christophe.jaillet@wanadoo.frSigned-off-by: Vinod Koul <vkoul@kernel.org>