arch: arm64: Fix ICC_SGI1R mask for arm64

According to "Arm A-profile Architecture Registers",
Interrupt Controller Software Generaated Interrupt
Group 1 Register (ICC_SGI1R), AFF is 8 bits width
and the mask should be 0xFF but not 0xF.

Cortex_a_r is okay and no need to be fixed.

Signed-off-by: Steven Shen <steven.shen@jaguarmicro.com>
Tested-by: Rex Nie <rex.nie@jaguarmicro.com>