rtl818x: Replace mdelay() with msleep() in rtl8225se_rf_init

rtl8225se_rf_init() is never called in atomic context.
It calls mdelay() to busily wait, which is not necessary.
mdelay() can be replaced with msleep().
This patch only replaces the mdelay() that has >20ms time to wait.

This is found by a static analysis tool named DCNS written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>