PCI_LOONGSON is a mandatory for LoongArch and it is selected in Kconfig
unconditionally, but its dependency PCI_QUIRKS is missing and may cause
a build error when "make randconfig":

   arch/loongarch/pci/acpi.c: In function 'pci_acpi_setup_ecam_mapping':
>> arch/loongarch/pci/acpi.c:103:29: error: 'loongson_pci_ecam_ops' undeclared (first use in this function)
     103 |                 ecam_ops = &loongson_pci_ecam_ops;
         |                             ^~~~~~~~~~~~~~~~~~~~~
   arch/loongarch/pci/acpi.c:103:29: note: each undeclared identifier is reported only once for each function it appears in

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for PCI_LOONGSON
   Depends on [n]: PCI [=y] && (MACH_LOONGSON64 [=y] || COMPILE_TEST [=y]) && (OF [=y] || ACPI [=y]) && PCI_QUIRKS [=n]
   Selected by [y]:
   - LOONGARCH [=y]

Fix it by selecting PCI_QUIRKS unconditionally, too.
Reported-by: kernel test robot <lkp@intel.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>