PCI: rzg3s-host: Drop the lock on RZG3S_PCI_MSIRS and RZG3S_PCI_PINTRCVIS

PCI: rzg3s-host: Drop the lock on RZG3S_PCI_MSIRS and RZG3S_PCI_PINTRCVIS

The RZG3S_PCI_MSIRS and RZG3S_PCI_PINTRCVIS registers are of the R/W1C
type. According to the RZ/G3S HW Manual, Rev. 1.10, chapter 34.2.1
Register Type, R/W1C register bits are cleared to 0b by writing 1b, while
writing 0b has no effect. Therefore, there is no need to take a lock
around writes to these registers.

Drop the locking.

Along with this, add a note about the R/W1C register type to the register
offset definitions.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://patch.msgid.link/20251217111510.138848-3-claudiu.beznea.uj@bp.renesas.com