x86/mce: Remove unused variable and return value in machine_check_poll()

x86/mce: Remove unused variable and return value in machine_check_poll()

The recent CMCI storm handling rework removed the last case that checks
the return value of machine_check_poll().

Therefore the "error_seen" variable is no longer used, so remove it.

Fixes: 3ed57b41a412 ("x86/mce: Remove old CMCI storm mitigation code")
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240523155641.2805411-3-yazen.ghannam@amd.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>