[build] Remove unnecessary constraint on DBG_ENABLE()/DBG_DISABLE()

DBG_ENABLE() and DBG_DISABLE() are currently constrained to enabling
and disabling only debug levels that are compiled in for the current
object.  For example, a DBG_ENABLE(DBGLVL_EXTRA) in foo.c will not be
able to affect output from other objects at DBGLVL_EXTRA unless foo.c
is itself compiled with DBGLVL_EXTRA enabled.

Partially fix by removing this unnecessary constraint.  (Note that it
is still necessary for at least one debug level to be compiled in for
the object invoking DBG_ENABLE()/DBG_DISABLE().)

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/compiler.h

@@ -286,10 +286,10 @@ extern void dbg_more ( void );
 int __debug_disable;
 #define DBGLVL ( DBGLVL_MAX & ~__debug_disable )
 #define DBG_DISABLE( level ) do {				\
-	__debug_disable |= ( (level) & DBGLVL_MAX );		\
+	__debug_disable |= (level);				\
 	} while ( 0 )
 #define DBG_ENABLE( level ) do {				\
-	__debug_disable &= ~( (level) & DBGLVL_MAX );		\
+	__debug_disable &= ~(level);				\
 	} while ( 0 )
 #else
 #define DBGLVL 0