hugetlb: fix hugepages= entry in kernel-parameters.txt

The hugepages= entry in kernel-parameters.txt states that 1GB pages can
only be allocated at boot time and not freed afterwards.  This is not
true since commit 944d9fec8d ("hugetlb: add support for gigantic page
allocation at runtime"), at least for x86_64.

Instead of adding arch-specifc observations to the hugepages= entry,
this commit just drops the out of date information.  Further information
about arch-specific support and available features can be obtained in
the hugetlb documentation.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/kernel-parameters.txt

@@ -1228,9 +1228,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			multiple times interleaved with hugepages= to reserve
 			huge pages of different sizes. Valid pages sizes on
 			x86-64 are 2M (when the CPU supports "pse") and 1G
-			(when the CPU supports the "pdpe1gb" cpuinfo flag)
-			Note that 1GB pages can only be allocated at boot time
-			using hugepages= and not freed afterwards.
+			(when the CPU supports the "pdpe1gb" cpuinfo flag).
 
 	hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
 			       terminal devices. Valid values: 0..8