x86: Rename pcat_ to i8254 and i8259 accordingly

Rename pcat_timer.c to i8254.c and pcat_interrupts.c to i8259.c,
to match their header file names (i8254.h and i8259.h).

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/include/asm/u-boot-x86.h b/arch/x86/include/asm/u-boot-x86.h
index 1c459d5..dbf8e95 100644
--- a/arch/x86/include/asm/u-boot-x86.h
+++ b/arch/x86/include/asm/u-boot-x86.h
@@ -29,7 +29,7 @@
 int register_timer_isr (timer_fnc_t *isr_func);
 unsigned long get_tbclk_mhz(void);
 void timer_set_base(uint64_t base);
-int pcat_timer_init(void);
+int i8254_init(void);
 
 /* cpu/.../interrupts.c */
 int cpu_init_interrupts(void);