drivers: ata: Mark the function ahci_init_interrupts() as static in ahci.c
This patch marks the function ahci_init_interrupts() as static in ahci.c
because it is not used outside this file.
Thus, it also eliminates the following warning in ahci.c:
drivers/ata/ahci.c:1099:5: warning: no previous prototype for ‘ahci_init_interrupts’ [-Wmissing-prototypes]