ArmPkg: Fix Ecc error 9005 in CpuDxe

ArmPkg: Fix Ecc error 9005 in CpuDxe

This patch fixes the following Ecc reported error:
Only Doxygen commands '@bug', '@todo', '@example', '@file',
'@attention', '@param', '@post', '@pre', '@retval', '@return',
'@sa', '@since', '@test', '@note', '@par', '@endcode', '@code',
'@{', '@}' are allowed to mark the code

This patch removes the ":" character following the "@param"
doxygen command.

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>