ptp_qoriq: don't pass a large struct by value but instead pass it by reference

Passing the struct ptp_clock_info caps by parameter is passing over 130 bytes
of data by value on the stack. Optimize this by passing it by reference instead.
Also shinks the object code size:

Before:
   text	   data	    bss	    dec	    hex	filename
  12596	   2160	     64	  14820	   39e4	drivers/ptp/ptp_qoriq.o

After:
   text	   data	    bss	    dec	    hex	filename
  12567	   2160	     64	  14791	   39c7	drivers/ptp/ptp_qoriq.o

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>