net: hns3: add new function hclge_get_speed_bit()

mainline inclusion
from mainline-v5.15-rc1
commit aec35aec
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4BY3P
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aec35aecc3ccc822b358e2594ff70ff54245261e



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Currently, function hclge_check_port_speed() uses switch/case statement
to get speed bit according to speed. To reuse this part of code and
improve code readability and maintainability, add a new function
hclge_get_speed_bit() to get speed bit according to map relationship
of speed and speed bit defined in array speed_bit_map.

Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Yongxin Li <liyongxin1@huawei.com>
Signed-off-by: Junxin Chen <chenjunxin1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>