watchdog: sbsa: Update the W_IIDR Implementer bit mask to 0xFFF

The implementer mask defined in the driver [1] captures bits 0-10,
whereas section C.4.2 of BSA specification [2] indicates that bits
0-11 of the W_IIDR register represent the implementer JEP106 code.
Update the SBSA_GWDT_IMPL_MASK corresponding to bits 0-11, while
at it update SBSA_GWDT_VERSION_MASK mask to use GENMASK.

[1] #define SBSA_GWDT_IMPL_MASK 0x7FF

[2] Implementer, bits [11:0]
Contains the JEP106 code of the company that implemented the
Generic Watchdog:
Bits[11:8] The JEP106 continuation code of the implementer.
Bit[7] Always 0
Bits [6:0] The JEP106 identity code of the implementer.

Signed-off-by: Naina Mehta <naina.mehta@oss.qualcomm.com>
Acked-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>