libcamera: Add missing <stdint.h> include to base/file.h

Without the change the build fails on upcoming `gcc-15` as:

    In file included from ../src/libcamera/base/file.cpp:8:
    ../include/libcamera/base/file.h:62:33: error: 'uint8_t' was not declared in this scope
       62 |         ssize_t read(const Span<uint8_t> &data);
          |                                 ^~~~~~~

Signed-off-by: Sergei Trofimovich <slyich@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>

include/libcamera/base/file.h

@@ -7,6 +7,7 @@
 
 #pragma once
 
+#include <stdint.h>
 #include <sys/types.h>
 
 #include <map>