libcamera: base: log: Fix uninitialized variable warning

gcc 13.3.0, cross-compiling from amd64 to arm64, warns about a possibly
uninitialized variable in Logger::parseLogLevel():

src/libcamera/base/log.cpp: In static member function ‘static libcamera::LogSeverity libcamera::Logger::parseLogLevel(std::string_view)’:
../../src/libcamera/base/log.cpp:694:55: error: ‘severity’ may be used uninitialized [-Werror=maybe-uninitialized]
  694 |                 if (ec != std::errc() || *end != '\0' || severity > LogFatal)
      |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
src/libcamera/base/log.cpp:690:22: note: ‘severity’ was declared here
  690 |         unsigned int severity;
      |                      ^~~~~~~~

This appears to be a false positive, as the std::from_chars() function
should set severity value when it returns without an error. Still, the
warning is easy to solve, so fix it by initializing the severity
variable.

Fixes: 8fa119e0b5 ("libcamera: base: log: Use `std::from_chars()`")
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/base/log.cpp

@@ -687,14 +687,13 @@ LogSeverity Logger::parseLogLevel(std::string_view level)
 		"FATAL",
 	};
 
-	unsigned int severity;
+	unsigned int severity = LogInvalid;
 
 	if (std::isdigit(level[0])) {
 		auto [end, ec] = std::from_chars(level.data(), level.data() + level.size(), severity);
 		if (ec != std::errc() || *end != '\0' || severity > LogFatal)
 			severity = LogInvalid;
 	} else {
-		severity = LogInvalid;
 		for (unsigned int i = 0; i < std::size(names); ++i) {
 			if (names[i] == level) {
 				severity = i;