misc: ti-st: make array read_ver_cmd static, shrinks object size

Don't populate the const array read_ver_cmd on the stack but instead
make it static. Makes the object code smaller by 42 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  17262	   6928	    192	  24382	   5f3e	drivers/misc/ti-st/st_kim.o

After:
   text	   data	    bss	    dec	    hex	filename
  17156	   6992	    192	  24340	   5f14	drivers/misc/ti-st/st_kim.o

(gcc version 8.2.0 x86_64)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>