staging: rtlwifi: rtl8822be: Use __func__ instead of hardcoded name

Switch hardcoded function name with a reference to __func__ making
the code more maintenable and addressing the checkpatch warning:

WARNING: Prefer using '"%s...", __func__' to using 'rtl8822be_sc_mapping', this function's name, in a string
+                                       "rtl8822be_sc_mapping: Not Correct Primary40MHz Setting\n");

Credits to checkpatch.

Signed-off-by: Frank A. Cancio Bello <frank@generalsoftwareinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>