rtlwifi: rtl_pci: Simplify some code be eliminating extraneous variables

In several places, the code assigns a variable inside an "if" or "case"
block, but uses it only once. The code is simplified by eliminating
the extraneous variable. With this change, one level of indenting is
saved.

This patch does not cause any functional changes in the binary code.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Ping-Ke Shih <pkshih@realtek.com>
Cc: Yan-Hsuan Chuang <yhchuang@realtek.com>
Cc: Birming Chiu <birming@realtek.com>
Cc: Shaofu <shaofu@realtek.com>
Cc: Steven Ting <steventing@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>