fix(pycardium): Ensure printf output is sent to Epicardium API

Previously, printf would output directly to UART, which led to race
conditions.  With removing card10-board from pycardium and implementing
_write() directly, this can be fixed.  Now printf & co will output via
Epicardium API.

Signed-off-by: Rahix <rahix@rahix.de>

pycardium/meson.build

@@ -71,9 +71,9 @@ elf = executable(
   modsrc,
   mp_headers,
   include_directories: micropython_includes,
-  dependencies: [max32665_startup_core1, board_card10, periphdriver, api_caller],
+  dependencies: [max32665_startup_core1, periphdriver, api_caller],
   link_with: upy,
-  link_whole: [max32665_startup_core1_lib, board_card10_lib],
+  link_whole: [max32665_startup_core1_lib],
   link_args: [
     '-Wl,-Map=' + meson.current_build_dir() + '/' + name + '.map',
   ],

pycardium/mphalport.c

@@ -41,6 +41,13 @@ int DEBUG_printf(const char *fmt, ...)
 	return ret;
 }
 
+/* newlib syscall to allow printf to work */
+long _write(int fd, const char *buf, size_t cnt)
+{
+	epic_uart_write_str(buf, cnt);
+	return cnt;
+}
+
 bool do_interrupt = false;
 
 /* Timer Interrupt used for control char notification */