imx: Use 'const char', not 'char const'

'char const' means the same thing as 'const char', but we
use the former in only a handful of places and we use the
latter over six thousand times. Switch the imx reg_name()
functions to bring them in line with everything else.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/hw/timer/imx_gpt.c b/hw/timer/imx_gpt.c
index f034d65..010ccbf 100644
--- a/hw/timer/imx_gpt.c
+++ b/hw/timer/imx_gpt.c
@@ -29,7 +29,7 @@
         } \
     } while (0)
 
-static char const *imx_gpt_reg_name(uint32_t reg)
+static const char *imx_gpt_reg_name(uint32_t reg)
 {
     switch (reg) {
     case 0: