[fedora-arm] Wiki gardening for aarch64

[Brendan Conoboy]

Hi everybody,

Adam Williamson mentioned to me that the Fedora wiki was missing an 
entry for Aarch64 on the secondary architecture list.  I've gone ahead 
and updated the architecture page:

https://fedoraproject.org/wiki/Architectures#Secondary_Architectures

To point to the standard ARM page.  By itself this isn't entirely 
satisfactory, since the ARM page itself is still largely 32-bit 
oriented.  Do we want to rework this page for greater aarch64 content or 
do we want to keep this an ARM32 page and add a distinct AArch64 page?