[IA64] mca.c: sparse cleanup

Looks like we were casting a value into a union and sparse doesn't like that.
Why not just assign it directly to the appropriate field?
Signed-off-by: Jesse Barnes <jbarnes@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/mca.c

@@ -593,7 +593,7 @@ ia64_mca_cmc_vector_disable (void *dummy)
 {
 	cmcv_reg_t	cmcv;
 
-	cmcv = (cmcv_reg_t)ia64_getreg(_IA64_REG_CR_CMCV);
+	cmcv.cmcv_regval = ia64_getreg(_IA64_REG_CR_CMCV);
 
 	cmcv.cmcv_mask = 1; /* Mask/disable interrupt */
 	ia64_setreg(_IA64_REG_CR_CMCV, cmcv.cmcv_regval);
@@ -620,7 +620,7 @@ ia64_mca_cmc_vector_enable (void *dummy)
 {
 	cmcv_reg_t	cmcv;
 
-	cmcv = (cmcv_reg_t)ia64_getreg(_IA64_REG_CR_CMCV);
+	cmcv.cmcv_regval = ia64_getreg(_IA64_REG_CR_CMCV);
 
 	cmcv.cmcv_mask = 0; /* Unmask/enable interrupt */
 	ia64_setreg(_IA64_REG_CR_CMCV, cmcv.cmcv_regval);