Fix a few gcc warnings.

Noticed while building all of mpc8xx. Also
constify usage string in timer.c
Warnings fixed are:
timer.c: In function 'timer':
timer.c:189: warning: format not a string literal and no format arguments
timer.c:258: warning: format not a string literal and no format arguments
atm.c: In function 'atmUnload':
atm.c:99: warning: array subscript is above array bounds
atm.c: In function 'atmLoad':
atm.c:65: warning: array subscript is above array bounds
codec.c: In function 'codsp_write_pop_int':
codec.c:678: warning: array subscript is above array bounds
codec.c: In function 'codsp_write_cop_short':
codec.c:585: warning: array subscript is above array bounds
codec.c: In function 'codsp_write_sop_int':
codec.c:512: warning: array subscript is above array bounds

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
diff --git a/board/siemens/IAD210/atm.c b/board/siemens/IAD210/atm.c
index e599c10..40aad0a 100644
--- a/board/siemens/IAD210/atm.c
+++ b/board/siemens/IAD210/atm.c
@@ -62,7 +62,7 @@
   volatile iop8xx_t      *iop    = &immap->im_ioport;
 
   timers->cpmt_tgcr &=  0x0FFF; SYNC;             /* Disable Timer 4 */
-  immap->im_cpm.cp_scc[4].scc_gsmrl = 0x0; SYNC; /* Disable SCC4 */
+  immap->im_cpm.cp_scc[3].scc_gsmrl = 0x0; SYNC; /* Disable SCC4 */
   iop->iop_pdpar &= 0x3FFF; SYNC;                 /* Disable SAR and UTOPIA */
 
   if ( atmMemInit() != OK ) return ERROR;
@@ -96,7 +96,7 @@
   volatile iop8xx_t      *iop    = &immap->im_ioport;
 
   timers->cpmt_tgcr &=  0x0FFF; SYNC;             /* Disable Timer 4 */
-  immap->im_cpm.cp_scc[4].scc_gsmrl = 0x0; SYNC;  /* Disable SCC4 */
+  immap->im_cpm.cp_scc[3].scc_gsmrl = 0x0; SYNC;  /* Disable SCC4 */
   iop->iop_pdpar &= 0x3FFF; SYNC;                 /* Disable SAR and UTOPIA */
   g_atm.loaded = FALSE;
 }