staging: rtl8723bs: Rename supportRate and SupportRateNum to snake_case

staging: rtl8723bs: Rename supportRate and SupportRateNum to snake_case

renamed variables supportRate and supportRateNum to support_rate and
support_rate_num to adhere to the linux kernel coding style which mandates
snake_case for variable names.

This fixes the following checkpatch.pl warning:
    CHECK: Avoid CamelCase: <supportRate>
    CHECK: Avoid CamelCase: <supportRateNum>

Signed-off-by: Matous Jarolim <matous.jarolim.lkml@gmail.com>
Link: https://patch.msgid.link/20260113170346.557634-1-matous.jarolim.lkml@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>