PCI: brcmstb: Do not assume that register field starts at LSB

PCI: brcmstb: Do not assume that register field starts at LSB

When setting the LNKCAP and LNKCTL2 register fields, it was assumed
that the field started at the LSB of the register.

Although the masks do indeed start at the LSB, and this will probably
not change, it is prudent to use a method that makes no assumption
about the mask's placement in the register.

Thus, use the u{16,32}p_replace_bits() helpers since they are already
wildly used in this driver.

Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20250214173944.47506-4-james.quinlan@broadcom.com
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>