drm/i915/perf: remove redundant variable 'taken'

The assignment to variable taken is redundant and so it can be
removed as well as the variable too.

Cleans up clang-scan build warnings:
warning: Although the value stored to 'taken' is used in the enclosing
expression, the value is never actually read from 'taken'
[deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221007195345.2749911-1-colin.i.king@gmail.com