stdio: extend "name" to 32 symbols

With limit of 16 symbols very simple device names derived drom device
tree description could not be displayed correctly.

For example "serial0@0xc0fc1000" will be truncated to sensless
"serial0@0xc0fc10" - note dropped tariling zeros.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>