Why we need CapsuleLib even platform does not support this feature

[Udit Kumar <udit.kumar@nxp.com>]

Hi, 
I recently noticed in my build as well, we need to include CapsuleLib even platform does not support Capsule update feature. 
Thanks to help me, why this dependency is added in edk2. 

Regards
Udit

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard
> Biesheuvel
> Sent: Tuesday, November 14, 2017 4:48 PM
> To: Kalyan Nagabhirava <kalyankumar.nagabhirava@linaro.org>
> Cc: edk2-devel@lists.01.org; Leif Lindholm <leif.lindholm@linaro.org>; Mark
> Gregotski <mark.gregotski@linaro.org>
> Subject: Re: [edk2] [PATCH edk2-platforms]: resolving Hikey platform build error
> 
> On 14 November 2017 at 11:16, Kalyan Nagabhirava
> <kalyankumar.nagabhirava@linaro.org> wrote:
> >
> > "Instance of library class [CapsuleLib] is not found" build error is
> > coming for Hikey platform, to resolve this issueadded CapsuleLib to
> > "LibraryClasses.common" section
> >
> > diff --git a/Platform/Hisilicon/HiKey/HiKey.dsc
> > b/Platform/Hisilicon/HiKey/HiKey.dsc
> > index 968e8ac..2e3b1c8 100644
> > --- a/Platform/Hisilicon/HiKey/HiKey.dsc
> > +++ b/Platform/Hisilicon/HiKey/HiKey.dsc
> > @@ -61,6 +61,7 @@
> >
> > SynchronizationLib|MdePkg/Library/BaseSynchronizationLib/BaseSynchroni
> > SynchronizationLib|zationLib.inf
> >
> >    FdtLib|EmbeddedPkg/Library/FdtLib/FdtLib.inf
> > +
> > + CapsuleLib|MdeModulePkg/Library/DxeCapsuleLibNull/DxeCapsuleLibNull.
> > + inf
> >
> >
> UefiBootManagerLib|MdeModulePkg/Library/UefiBootManagerLib/UefiBootM
> an
> > UefiBootManagerLib|agerLib.inf
> >
> >
> PlatformBootManagerLib|ArmPkg/Library/PlatformBootManagerLib/PlatformB
> > PlatformBootManagerLib|ootManagerLib.inf
> >    BootLogoLib|MdeModulePkg/Library/BootLogoLib/BootLogoLib.inf
> >
> >
> 
> Thanks Kalyan
> 
> Could you resend it as a proper patch, please? I.e., with the appropriate
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> 
> and Signed-off-by line,
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