tests: fat: fat_fs_api reduce the wipe partition sectors

As SD partition tables, GPT or MBT, is positioned at
the beginning of a device, it is enough to wipe first 64 sectors,
of 512 bytes. Wipe of entire SD card is very slow and unnecessary.

fixes: #84428

Signed-off-by: Hake Huang <hake.huang@oss.nxp.com>