riscv: cpufeature: Drop errata_list.h and other unused includes

Drop errata_list.h, since cpufeature.c includes hwcap.h directly to
get cpufeature IDs. And, while there, prune the rest of the unused
includes too.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Link: https://lore.kernel.org/r/20230224154601.88163-7-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Andrew Jones

arch/riscv/kernel/cpufeature.c

@@ -8,20 +8,15 @@
 
 #include <linux/bitmap.h>
 #include <linux/ctype.h>
-#include <linux/libfdt.h>
 #include <linux/log2.h>
 #include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <asm/alternative.h>
 #include <asm/cacheflush.h>
-#include <asm/errata_list.h>
 #include <asm/hwcap.h>
 #include <asm/patch.h>
-#include <asm/pgtable.h>
 #include <asm/processor.h>
-#include <asm/smp.h>
-#include <asm/switch_to.h>
 
 #define NUM_ALPHA_EXTS ('z' - 'a' + 1)