configs/galileo_defconfig: add missing double quotes around BR2_GLOBAL_PATCH_DIR value

This bogus BR2_GLOBAL_PATCH_DIR value was added in commit
9dd5382d ("board/intel/galileo: fix
build failure with host gcc 10") back in February.

This should help fixing
https://gitlab.com/buildroot.org/buildroot/-/jobs/2781800667

, as it
complains with:

WARN: defconfig ./configs/galileo_defconfig can't be used:
      Missing: BR2_GLOBAL_PATCH_DIR=board/intel/galileo/patches

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>