PCI: qcom: Define slot capabilities using PCI_EXP_SLTCAP_*

The PCIE_CAP_LINK1_VAL macro actually defines slot capabilities. Use
PCI_EXP_SLTCAP_* macros to spell its value, and rename it to better
describe its meaning.

Link: https://lore.kernel.org/r/3025d5e1d8da64798db6958f9780c4763fbcac47.1655799816.git.baruch@tkos.co.il


Signed-off-by: Baruch Siach <baruch.siach@siklu.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Stanimir Varbanov <svarbanov@mm-sol.com>