android: add a warning about SD card problems

We have observed that Android can get confused when an SD Card is present while booting from eMMC:

[    0.858548][    T1] init: bool android::init::BlockDevInitializer::InitDevices(std::set<std::string>): partition(s) not found in /sys, waiting for their uevent(s): boot_b, init_boot_b, metadata, persist, super
[    0.858722][   T49] printk: console [ttyS2] enabled
[    3.914029][   T49] rtc-ti-k3 2b1f0000.rtc: registered as rtc0
[    3.919968][   T49] rtc-ti-k3 2b1f0000.rtc: setting system clock to 1970-01-01T00:00:10 UTC (10)
[    3.931694][   T10] mmc0: CQHCI version 5.10
[    3.937915][   T49] tps6598x 0-003f: Unable to find the interrupt, switching to polling
[    3.946857][   T49] pca953x 1-0022: supply vcc not found, using dummy regulator
[    3.954572][   T49] pca953x 1-0022: using AI
[    3.977885][   T10] mmc0: SDHCI controller on fa10000.mmc [fa10000.mmc] using ADMA 64-bit
[   10.866870][    T1] init: Wait for partitions returned after 10003ms
[   10.873338][    T1] init: bool android::init::BlockDevInitializer::InitDevices(std::set<std::string>): partition(s) not found after polling timeout: boot_b, init_boot_b, metadata, persist, super
[   10.891069][    T1] init: Failed to mount required partitions early ...

To avoid any problems, document that we should remove it.

Signed-off-by: Mattijs Korpershoek mkorpershoek@baylibre.com