Remove misc NULL checks after M_WAITOK allocations.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation

sys/dev/acpica/acpi_perf.c

@@ -267,8 +267,6 @@ acpi_perf_evaluate(device_t dev)
 
 	sc->px_states = malloc(sc->px_count * sizeof(struct acpi_px),
 	    M_ACPIPERF, M_WAITOK | M_ZERO);
-	if (sc->px_states == NULL)
-		goto out;
 
 	/*
 	 * Each state is a package of {CoreFreq, Power, TransitionLatency,

sys/dev/hwpmc/hwpmc_piv.c

@@ -605,9 +605,6 @@ p4_pcpu_init(struct pmc_mdep *md, int cpu)
 
 	p4c = malloc(sizeof(struct p4_cpu), M_PMC, M_WAITOK|M_ZERO);
 
-	if (p4c == NULL)
-		return (ENOMEM);
-
 	pc = pmc_pcpu[cpu];
 
 	KASSERT(pc != NULL, ("[p4,%d] cpu %d null per-cpu", __LINE__, cpu));

sys/dev/ioat/ioat.c

@@ -464,8 +464,6 @@ ioat3_attach(device_t device)
 
 	ioat->ring = malloc(num_descriptors * sizeof(*ring), M_IOAT,
 	    M_ZERO | M_WAITOK);
-	if (ioat->ring == NULL)
-		return (ENOMEM);
 
 	ring = ioat->ring;
 	for (i = 0; i < num_descriptors; i++) {

sys/dev/xen/evtchn/evtchn_dev.c

@@ -325,8 +325,6 @@ evtchn_write(struct cdev *dev, struct uio *uio, int ioflag)
 		return (EINVAL);
 
 	kbuf = malloc(PAGE_SIZE, M_EVTCHN, M_WAITOK);
-	if (kbuf == NULL)
-		return (ENOMEM);
 
 	count = uio->uio_resid;
 	/* Whole number of ports. */

sys/x86/xen/pv.c

@@ -226,8 +226,6 @@ start_xen_ap(int cpu)
 	bootAP = cpu;
 
 	ctxt = malloc(sizeof(*ctxt), M_TEMP, M_WAITOK | M_ZERO);
-	if (ctxt == NULL)
-		panic("unable to allocate memory");
 
 	ctxt->flags = VGCF_IN_KERNEL;
 	ctxt->user_regs.rip = (unsigned long) init_secondary;