wext: Fix musl build error
Building wpa_supplicant with the musl C library fails since musl does
not define type names such as '__uint32_t'. To support building
wpa_supplicant with the musl C library use the integer types declared in
the ISO C standard header file <stdint.h>.
Signed-off-by: Jörg Krause <jkrause@posteo.de>