Adds %c support for printf and snprintf to print one character. Required
by most recent MbedTLS 3.4.0.
Change-Id: I4d9b2725127a929d58946353324f99ff22b3b28b
Signed-off-by: Maksims Svecovs <maksims.svecovs@arm.com>
(cherry picked from commit 44d9706e54)