x86/platform/uv: Fix copied UV5 output archtype

A test shows that the output contains a space:
    # cat /proc/sgi_uv/archtype
    NSGI4 U/UVX

Remove that embedded space by copying the "trimmed" buffer instead of the
untrimmed input character list.  Use sizeof to remove size dependency on
copy out length.  Increase output buffer size by one character just in case
BIOS sends an 8 character string for archtype.

Fixes: 1e61f5a9 ("Add and decode Arch Type in UVsystab")
Signed-off-by: Mike Travis <mike.travis@hpe.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Link: https://lore.kernel.org/r/20201111010418.82133-1-mike.travis@hpe.com