LIB: tfm_vprintf: Add %i format specifier

Although %d is already present, extend with %i so it is
easier to introduce work-in-progress patches.

Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
Change-Id: I9637c514f44bf78c9a4acb3b3a4934fc72c01c8f
(cherry picked from commit 18c84d7)
Signed-off-by: Stefan Gloor <stefan.gloor@siemens.com>

Author: nicola-mazzucato-arm

lib/tfm_vprintf/src/tfm_vprintf.c

@@ -171,6 +171,7 @@ static void tfm_vprintf_internal(tfm_log_output_str output_func,
                        left_aligned, 10, false);
             break;
         case 'd':
+        case 'i':
             output_val(output_func, priv, va_arg(args, uint32_t), num_padding, zero_padding,
                        left_aligned, 10, true);
             break;