firmware-utils: seama: fix compiler warnings/errors

firmware-utils: seama: fix compiler warnings/errors

seama.c:334:16: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Werror=sign-compare]
seama.c:352:14: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Werror=sign-compare]
seama.c:374:13: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Werror=sign-compare]
seama.c:411:16: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Werror=sign-compare]
seama.c:438:16: error: comparison of integer expressions of different signedness: ‘size_t’ {aka ‘long unsigned int’} and ‘int’ [-Werror=sign-compare]
seama.c:453:4: error: ignoring return value of ‘fread’, declared with attribute warn_unused_result [-Werror=unused-result]
seama.c:469:4: error: ignoring return value of ‘fread’, declared with attribute warn_unused_result [-Werror=unused-result]
seama.c:473:5: error: ignoring return value of ‘fread’, declared with attribute warn_unused_result [-Werror=unused-result]

Signed-off-by: Petr Štetiar <ynezz@true.cz>