linuxkpi: Define raw_spinlock_t in <linux/spinlock.h>

For now, it is synonymous to `spinlock_t`. The DRM generic code uses the
`struct raw_spinlock` and not `raw_spinlock_t`, that's why the
definition is a struct embedding a `struct mtx`, compared to
`spinlock_t` which is a simpler typedef.

The DRM generic code started to use it in Linux 6.10.

Reviewed by:	bz, christos
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D54489

sys/compat/linuxkpi/common/include/linux/spinlock.h

@@ -178,4 +178,24 @@ _atomic_dec_and_lock_irqsave(atomic_t *cnt, spinlock_t *lock,
 	return (0);
 }
 
+/*
+ * struct raw_spinlock
+ */
+
+typedef struct raw_spinlock {
+	struct mtx	lock;
+} raw_spinlock_t;
+
+#define	raw_spin_lock_init(rlock) \
+	mtx_init(&(rlock)->lock, spin_lock_name("lnxspin_raw"), \
+	    NULL, MTX_DEF | MTX_NOWITNESS | MTX_NEW)
+
+#define	raw_spin_lock(rl)	spin_lock(&(rl)->lock)
+#define	raw_spin_trylock(rl)	spin_trylock(&(rl)->lock)
+#define	raw_spin_unlock(rl)	spin_unlock(&(rl)->lock)
+
+#define	raw_spin_lock_irqsave(rl, f)		spin_lock_irqsave(&(rl)->lock, (f))
+#define	raw_spin_trylock_irqsave(rl, f)		spin_trylock_irqsave(&(rl)->lock, (f))
+#define	raw_spin_unlock_irqrestore(rl, f)	spin_unlock_irqrestore(&(rl)->lock, (f))
+
 #endif					/* _LINUXKPI_LINUX_SPINLOCK_H_ */