riscv: cpufeature: use bitmap_equal() instead of memcmp()

riscv: cpufeature: use bitmap_equal() instead of memcmp()

Comparison of bitmaps should be done using bitmap_equal(), not memcmp(),
use the former one to compare isa bitmaps.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Fixes: 625034abd52a8c ("riscv: add ISA extensions validation callback")
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250210155615.1545738-1-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>